Currently, it's just the two of us, but I'll answer on our most recent V
1. Does anyone prefer certain things with certain partners?
Yes. Everyone has their strengths in the bedroom. My husband is not a kissy-cuddly sort of guy, my OSO was very much so. He and I could spend ages just cuddling and kissing, which is something that is very rare with my hubby.
2. Does anyone have more sex with one partner over another?
In our set up, hubby and I did have more sex than I had with OSO... it was purely logistics. OSO preferred to maintain a seperate household, and had other commitments outside of our V, so he wasn't around as much as my hubby is.
3. Does anyone in a "V" have threesomes with their partners?
Yes. Our V would occasionally have threesomes instead of one on one encounters. It worked for us.