I have the Thompson Peak (TP) with hipbelt. It really reminds me of the venerable Golite Breeze... I wouldn't be surprised at all if the maker had taken the Breeze and improved around it.
TP has a hipbelt and still manages to be lighter than the Breeze! This was accomplished by reducing the Breeze's ridiculously long extension collar, and using lighter fabric (which I think is robust enough for hauling up to 20 lbs.).
The TP hipbelt helps to stabilize your load. It doesn't transfer all that much weight. To me, it carries about the same as the Breeze -- maybe just slightly better.
Carrying in comfort, I think 20 lbs. is just about the maximum (15 lbs. is even better).