Okay, I just played through the game a few times and had a no sex run (as you can imagine it was boring and short), a no Mara or Kate run, a no Mara run, and a no Kate run. Obviously the scene at the park plays out differently with each of the last two runs. The no Kate run she shows up as usual but Kate and Mara talk about how you could have had them both and shared, the No Mara run there is no sex at the park and nothing changes at dinner. Kate still talks about sharing and lesbian sex. The only change is she doesn't have anyone to send a picture to after dessert. The no Mara or Kate run you just have the blue sexual encounters and Becky.
I thought it was interesting to see how it did or didn't change. Honestly I think the No Mara or Kate run may be my favorite, the idea that the MC doesn't want anything longterm or even remotely serious makes sense so I have him deciding to avoid fucking his bf's daughter and sister in his house.
Anyway, I look forward to seeing what happens next and maybe getting a piece of Rayne in an update or so.