3 is too little, 4 is just right, but I think 5 is the best. Got it from my love for Ouran High School Host Club and La Corda D'oro, I could have more than one love interest if there's much more LI's in the game!
Five is perfect! Anything more makes me feel like their story length would be shortened to compromise or is otherwise overwhelming if you have a completionist mindset. It's honestly one of the reasons why I was put off from 9 R.I.P for so long... (praise me, I've finally started it this spooky season just so I don't come off as a larper for the official cupsleeve event HAHA)
I think 5 is bare minimum! Especially because at least 1 is gonna be childhood friend (I'm very tired about this TBH so it auto cancels out a route for me...) So at least 5 is good for me~ I like variety so long as it does not sacrifice writing~