2 - yes, VS = Variable Speed, VSF = Variable Speed/Flow. Go with the recommendations from PJT on models, 011028 (VS) and 011056 (VSF).
3 - Agree that more is better, I have 4 total, 1 Spa 3 pool, and if I did it again, I would add 2 more.
Also, depending on how much sun your pool gets...