From my personal experince with the game, I highly recommend you to try to pursue and see all the different paths/girls the story has to offer. Who knows? Your opinion on a certain character might do a total 180 and you'll end up liking themway more than when you started playing. (And I say this as someone who doesn't like Felicia all that much) .
Regarding the Mina stuff, it's up to how each player wants to see it. Personally I don't see it much as "stealing" since Killian admits himself to not give that much of a crap about their relationship (It's still cheating, though) . If it bothers you
You can always make Edwin get with her after the two of them break up if your affection score is high enough.
Eyyy, finally someone shares my opinion about this scene