The characters are all from the game Honkai Impact 3rd with a few exceptions from the honkai manga and some originals...
That's a good question, in the original game the main story does have a yuri atmosphere, but that won't be the case here... (it will be completely replaced by a shoujo-ai focused only on friendship between the girls and romance only with the protagonist), I particularly love yuri to the point of having characters that I consider untouchable by a man like Enterprise and Belfast (seriously, it makes me sick to see these two if they're not with each other) but now back to the point...
Although I love yuri, I just can't stand it in honkai, so there won't be any... The most that can happen are those light interactions during a threesome, foursome or more just heat-of-the-moment things without any romantic feelings involving the girls.
As for the music, I think I've been told about this before, but I always end up forgetting because I play without audio, but I've already thought about using one of the songs from the original, one that isn't too annoying, so I'll look into that later.