I don't usually full clear a game before starting a new one. For me, it really depends on whether the plot is interesting. If I find the story boring, I'll just drop it and move on to the next game without finishing it.
I never really noticed that before. I'm usually just focused on the plot. That said, I guess having more choices could mean more branching paths and content to explore?
I don't think I have a strict preference. My first BL game was DRAMAtical Murder, so I kind of got used to the MC being the bottom by default. However, I find that a bisexual MC who can be both a top and a bottom leaves a much deeper impression on me.