I've been looking for a nice set of aftermarket wheels for awhile and i think this time i have found the ones i really want. The thing is i'm no wheel expert, so i need some advice on wheel offset. These rims come in two different offsets. A "0" and a "+20" offset. Can someone help me understand this and help choose the right offset for my Supercrew.

Also the wheels are a one piece cast aluminum chrome plated. Is that good or not also?