I hope it's okay for me to answer. And I'm sorry for how messy and scattered and LONG my writing is (is there a way to hide it under a cut?).
Romance with the LI/ROs:
I do not self-insert at all, so I view it like watching a romantic drama or reading a romance novel (or just any type of story). Even if self-inserting is encouraged (like if there is customisation), I still do not, and always view the MC as a separate character from me. I honestly can't self-insert and I don't even want to, especially because I am aroace so I wouldn't want to personally even be in those situations lmao. But even outside of that, I just derive the most enjoyment from seeing the story from a third-person perspective, because I like seeing how two characters interact with each other, how their individualities and backgrounds and lives so far influence the way their relationship develops. And what themes the writer is trying to convey through these different dynamics between the MC and each route's love interest, as well as the overall narrative. Because I view it this way, I (personally) find it important to view all the characters, including the MC, as characters independent from me so that I can analyse their characterisation more objectively and see how the settings (personality, etc) decided by the writer are important in what they are trying to convey.
Seeing the MC as a separate character also allows me to emotionally connect with her better because then I can more easily (from an external view) see and think through her psychology, emotions and feelings and it helps me understand her perspective and empathise with her more. It makes me feel happy and more immersed in the story to be able to read through her point of view and see what her changing thoughts on everything are, especially if they're explained well in a detailed way. I love witnessing her development and emotional journey and it makes me feel genuinely moved to be able to see it. The happy ends and romance feel so earned and fulfilling because of how invested I am in her arc and character. So I like viewing her as a separate character because it personally helps me see her better both emotionally and analytically.
It's honestly really fun for me to wonder why the writer decided to make the MC this way, or make her act in this way and how that contributes to the overall story or what I think the writer is trying to say. To me, MCs/heroines are the most important character because they are the main character, so they should be the ones representing and driving the main themes of the work. Because of how important I think they are (or should be) to the story, they end up kind of representing the entire story, and my love for the work becomes almost predicated on them. And as the POV character, they (as an overall character, their development, their feelings, their thoughts, etc) should be compelling because I'm always in their head and seeing their perspective. They make or break a story for me because of these reasons. I have to love them (more than any of the other characters) in order to love the rest of the story. The more defined and carefully depicted their thoughts/feelings are, the more immersive I find it because of how real they feel.
And because MCs are so important and integral to me enjoying the story, I would never want to replace them with myself, since I am not a character and would most likely not fit into the story anyway (and I personally feel bothered and my immersion is broken when a story doesn't make sense to me or there are things that I feel are anachronistic, don't fit, etc). The otome games that resonate most deeply with me are the ones that focus on telling a very tight and thematically coherent story, and that usually requires all the characters, including the MC, to be very precisely a certain way, and that is something that I would not be able to replicate if I was the MC (because I am a real person and not literally created for this story to fit its specific themes). Especially because otome games are romance games, so human relationships are the main point and the dynamic between the MC and the love interests is very important. I think it is difficult to create a compelling dynamic, or even just the specific dynamic you need for the story, if both characters aren't defined or set to be a certain way (so I don't want to replace that). And I just love many otome MCs, which is why I wouldn't want to ever replace them with myself. That would feel like I'm erasing my favourite character haha. Basically, I personally am someone who just wants to see the story the writer wants to tell and the themes/messages they want to convey using these characters.
Having said all this, I want to emphasise that this is all my personal opinion/view of things and that all ways of viewing a story and playing a game are valid.
Morality:
I separate it from reality as I am not playing as myself, but instead in the point of view of the MC. So the choices I pick are the ones I think she would pick or that make sense for her personality (or for what the story is setting up), regardless of my view on the morality of these choices. I do end up feeling guilty and reluctant to pick some choices that I morally don't agree with too much, but if it fits the character, I will ultimately pick it (and I am a completionist so I will look at all the choices eventually). But to be honest, many heroines are portrayed as kind and quite morally pure anyway, so I rarely find that it makes sense for them to pick options that are too morally bad. And by the end of the story, especially for happy ends, usually kinder choices are more heartwarming and fit the message/the character's development at that point anyway so I don't really have reasons to pick some of the morally worse options (outside of completionism/seeing what they do - although I like morally grey choices when they fit and also really like bad ends that make sense, so if it's like a bad end corruption arc type of thing, I will happily pick them). In games in general, some of the "evil" choices seem to make less sense in general and sometimes seem almost comically over the top that I can't imagine it would psychologically make sense for any character to pick them, and that's why I usually do not. But again, if it actually makes sense, I will pick them even if it's against my personal, real life morality (which I can separate because I am not playing as myself and view it as fiction).
MC Customisation:
I view the MC as her own character, so I personally don't want customisation, whether appearance or personality (and I feel burdened by having to do it, to be honest, when I just want to read the story). I think even choices are something I don't particularly need (unless that in itself is thematically important), because I just want to experience the story written and designed by the writer (and if the MC is more of a defined character, it's obvious that it makes more sense for the MC to act in a specific way so I feel like choices can weaken that or some of them can feel OOC as a result). The more control I have, the less (creative) control the writer has, which in my opinion, would weaken the story they can tell, because then they cannot pick an angle or focus on telling a tight story with specific themes. They will have to make things more generic to fit all the options, and they'll be unable to flesh out any particular option to its full potential. I think trying to do everything or cater to everything means catering to nothing particularly well, as you cannot give as much attention to any one thing, or do any single thing as well or with as much depth compared to if only that one thing was concentrated on. And if you have to write to accommodate too many choices (whether personality or just any choice/option in general), you can't focus on telling one, particularly strong story (for each route) or theme. And this isn't just for choices/writing but just general logistics as well - trying to do/make too many things (or add too many features) in a game or work means fewer resources/less time for each individual thing.
Sometimes, certain choices and options also don't make sense or feel to me like they result in a weaker story if you pick them because the writer clearly wants to tell one particular story (which is normal and necessary because this is still just one overall story after all) and some of the choices just inherently align better with that and those themes. Therefore, I prefer fewer choices because it's true that certain things will fit the themes better, and I would rather the writer just show me a good story instead of trying to make me guess what would result in one. Because I care a lot about the themes of a story and having them feel cohesive (like every aspect of the story contributes to the overall theme), I want the writer to have enough control that they are able to craft all aspects to fit these themes, and to strongly deliver their message. I feel like the more say I have, the more the writer has to diminish the purity of their message/authorial intent, which is why I basically would rather just see the story they're trying to tell without as much input on my end. And I wouldn't be able to predict what the writer intends or wants to say so I wouldn't be able to decide what would lead to that or enhance those themes. I guess I generally prefer a more linear story that feels satisfying and resolves everything well, instead of accidentally choosing things that give me a less satisfying experience.
Even though appearance technically isn't part of the writing (so it may not matter as much), character design is still important to me, so I would prefer if the MC (just like the other characters), is designed by a professional character designer that creates a design that fits the setting, her character and her role in the story. I'm not a character designer and this isn't my story (I did not write it), so I feel like I wouldn't be able to create an actually good design that fits lmao. Because even if this isn't technically part of the writing, the design still has story implications (so is still important to me), connotating different things about the character, allowing for symbolism, etc. At least, I would want the design to make sense for the MC and to fit who they are and their place in the world, as well as how they are viewed by others in the story/setting (eg, if they are supposed to stand out, or conversely, blend in or be "invisible" in the crowd, I would want that to be reflected in the design because I think it would enhance the overall storytelling and make it more consistent to me).
If there is customisation, things like this would not be able to be taken into consideration, and because I am not the writer/devs and do not know what story they want to tell (especially before playing which is when customisation is), I would be unable to create a design that fits who the character is (because I don't know) and fits what the story ends up as/the intended themes. I feel like the people making it (writer, character designer, etc) would be able to create a more fitting design because they know the story they want to tell and what fits the MC they created. This is also why I like default names as someone who doesn't self-insert, because not only is it difficult to come up with names (that I think fit the MC before I even know what she's like), but especially for things like fantasy worlds, I have no idea what type of name would even fit the lore or the world. Anyway, in terms of logistics, customisation makes it difficult to have the MC appear in CGs and other artwork (and I'd feel so bad because of the artist's exponentially increased workload) - even if they do, I feel like the overall art might be weakened because the artist would not be able design the entire composition, etc, to fit the design as there isn't a set design (or it would just be limited to poses or compositions that mostly hide the MC still).
If personality is customisable, I feel like this could weaken the dynamic between the love interest and the MC (for me personally) because not all personality types would fit the intended dynamic of the relationship/route, or the dynamic would change into something that no longer worked with this particular story so would require a whole different one with different relationship build up and development. It's true that maybe multiple dynamics could be written, but that would basically require the writer to write multiple stories as the relationship would be different (because otome games focus on relationships, the relationship is basically the heart of the story so a different relationship would result in a different story with different themes, different relationship development path and thus a whole different route, etc) instead of just the one they want to tell. Sometimes, different personality types would just result in completely different things happening, and the story would become entirely different, preventing the writer from telling the story they want. And it's okay, not all otome games are trying to tell a super specific story, as some may want to focus on being a more sandbox-like experience which is completely valid. It's just that I personally prefer to experience a specific story designed by the writer. And because I view the MC as an independent character, I want her to have a set character, design and personality, just like the other characters.
RO Types or Preferences:
I am aroace as I said, so I don't have a real life type haha (or even a fictional type in terms of romance so I don't judge characters based on how good of a romantic partner I think they would be). So no character trope I like corresponds to my irl preferences because I don't have any. But if you're just talking about whether characters I like in these stories would be the types of people I would like to meet in real life, then the answer is also no, just because I don't judge characters based on how much I would like them if they were real people in real life. I usually like characters because they're interesting or I really enjoy how they are written, or admire how the writer crafted them to fit the story. Like how they interact and fit with the themes - I guess I kind of view it more in a writing perspective, like how much everything about them is crafted in relation to the story. But at the same time, sometimes I just like characters even if I don't think they're particularly well-written or anything (although if I liked them, then the writing did something right for me). Maybe something about them (something they did or something that happened to them?) just emotionally touched me or the themes they represent are ones I particularly resonate with.
But all this just means that I cannot map characters to literal real people, because real people obviously do not have "themes" and are not written a certain way because they are real, three dimensional people that characters could never be. I think that even though characters should feel like real people and psychologically make sense like them (and I do care about them and genuinely get emotionally attached to them), I fundamentally still view them differently from real life humans - as narrative tools first and foremost, so they're supposed to be a certain way, represent certain concepts (and simplified to do so), etc, in order to help tell the story. Therefore, I just cannot view them in a way that corresponds to my feelings toward real people. I don't even really have fictional types - in otome games, I usually (at least try to) like the entire cast of romance options because I view them and all their individual routes as important to the overall main theme or narrative of the overarching story. In fact, I feel like the contrast between different love interests helps to highlight the unique individuality each one has, as well as the themes and concepts each one represents (and how these all work together to make up the overall theme of the game).
This is ridiculously long and wordy and I'm sorry to everyone who read this (but thank you). I'm not even sure if this is okay to post. Anyway, I want to reiterate that this is all still my opinion (there is no better or worse way of enjoying things) and my personal way of enjoying otome games, and I am aware that it's probably very weird because of how much I focus on (and love) the MC, the writer's intentions and the craft of the story.
. I'm Chinese, and if you were to bring up this question in a Chinese otome game community, the replies would definitely turn into a battlefield. They wouldn't tolerate players who treat the heroine as an independent character in the game. If you dare to say that, they'll insult you, and they'll even pressure the game developers to say they don't welcome such players. If the developers don't comply, they'll be insulted too. They'll also discourage other players from trying the game, insult the heroine, saying she's just a shell for them to enter the game, a "camera" with no soul of her own, and that the male leads love the real-life version of themselves. They treat the heroine as a third party interfering in their relationship, claiming that otome games with heroines who have their own personalities aren't real otome games. (The above situation is most severe in Chinese mobile otome game communities.) That's why I usually don't dare to speak up in Chinese otome game communities. They don't think they're wrong, so I can only complain about their behavior privately with friends. 
Doesn't help that I download so many appearance and clothes custom content/mods...
