OK, nube question about wheels...

The stock size for the EX is 14", I think...

I want to get some ROTA style wheels, but see too many sizes...

I think I want the 15", because of price, and they are close to the stck size..

If I don't plan on showing the car, and only "race" occasionally (a minivan or station wagon here or there ), would a 40 or 45mm offset make a difference?

Would 16" wheels be better for the occasional "race"?

One more thing: Are hubcentric rings a MUST?

Thanks