If you increase the power of your car, you don't necessarily need to increase the wheel/tire sizing, it just helps out. If you go with big power, you'll want to increase the width of the rear tire essentially, that's the most important part since those are the driven wheels.
Poke refers to wheels sticking outside the fenders (see picture below). Poking is more for looks, not for function:
Pretty extreme example, but you get the idea
