Can I fit wide wheels (9"-9.5") or aggressive offset on a stock ride-height S2000 for track day without rubbing?

 

You can fit wide wheels but you will need really high offsets that are hard to find.

 

I guess what I meant was if the tires are sticking out of the fenderwells, will it rub with stock ride height?

 

depends on a lot of things. If it "sticks out" very moderately you should be fine. Why not just post up the setup you're looking at and we'll help you figure out how it'll fit. Depending on the setup, you can run up to a 285 tire out back, it's all in the offset.