I decided to get Rota Grid bronze for my civic, but dont know which size is better for appearance, will the size of the rims affect the gap between the fender and tires? thank you.

 

The size of the rim will not affect the overall fender clearance if you're talking 15s and 16s, as long as you get the proper size tires.

Now for looks and performance, I myself prefer the 16s, a nice blend of the two, without the strain of going overboard like one may with 17s. 16" gets my vote, but in the end it's all really up to you.

 

it usually depends on the rims but if your talking about the rota grids i'd go with 16's.