Quicksilver, you can still switch from low to high-res textures, its called "Half texture size." The only difference now is that you can't choose what resolution you want shown, either its full or half, back in S1 you could choose from 256 to 4096.
As far as work load goes, car models like his can take anywhere from one day to two weeks (two weeks being he took a trip 3/4ths of that time). Texturing on the other hand can take two or three weeks, and over a month to perfect.
Tracks on the other hand would take at least a month to complete (texturing as you go). And that doesn't even include the amount of thought and design that goes into it, and you have to figure out where to put bumps, where to put turns, altitude changes, the list goes on, making a track is difficult. But cars could be pumped out efficiently at 1 car each month.