I picked harem because I hate choosing. It's a bit strange I guess, but when it comes to porn games, I actually find branching paths super annoying(depending). The last thing I want to do after I finish a game is go back and do it again but this time hold ctrl until I get to a branch. I even, like a fool, often save at choices like I'm going to go back and try the other ones, but I almost never do. The exceptions are things like having a dom/sub path or other fetish specific splits like that as I'm generally not interested in the other path anyway. (God bless modders who add "both scene" options when devs force me to pick between two good options.)
Side note: You mention in OP a mechanism for adding custom characters. What's the process for that, do I just need a character card, or do I actually need to mod files?