What is the difference between Bones STF v5 and Bones OG v5 wheels?

Im looking to buy new wheels. People are saying that bones is a good wheel brand. So I have looked what to pick. And I came upon the STF and OG formula wheels, both Sidecut. On their website it says that side cut ones have more stabillity and less drag and longer grinds. Could someone explain what does drag mean? And could someone help me choose my wheel size? Im looking to buy 52 or 53mm which would be better?