When I did the numbers for my F150,i found the GVWR, GCWVR and maximum towing capacity all gave me around the same result. The GCWVR and maximum towing capacity were only possible without exceeding GVWR if there was only the driver, and no cargo, in the truck. Because I always have something in or on the truck, my GVWR results in the practical limit.
I am confused by curb weight. All the definitions I find state it is the weight of the vehicle with a full gas tank, all other fluids, but that it does not include the driver or any optional equipment. In my case that means around 400 pounds come off the cargo capacity for the cap and the driver. I need to get my truck manual to see if Ford rates it differently.
So, even though I have a 9600 pound towing capacity, I will exceed the GVWR at a much over trailer weight. Each case is different, but UT I would expect around 7000 pounds trailer weight to keep under the trucks rating.