Width and Length with Cargo Trailers and TC?

So, it looks like from reading cargo trailer specs that a 6 ft is 7'10" and 7, 8, or 8 1/2 cargo trailers are all 8'6". Is that what you've found, too? Did you go up or down in width and see an issue pulling behind your TC with either one width or the other? My thought is that longer would be slightly more difficult to make tighter turns and the same goes for more width.

I'm thinking 8 ft would be a lot more room, but seem to only come in longer trailers. I'm also considering a car hauler just in case I ever want to haul a car. I'm not sure of the tradeoffs other than the car hauler is obviously heavier.