In the RV world we think of a payload as the load that can be placed in the bed such as our truck campers or a GN/5th wheel trailer hitch load.
I keep harping on this point....the tire placard payload some folks use as a payload holy grail is a gvwr based payload and may overload some trucks rawr when its all placed in the bed.
The F150HD and the Titan XD is a good example.
Neither truck has the rear (rawr) to carry much over 2400-2500 lbs in the bed when actual math is done.
The Titan XD (4900 rawr)rear axle may weigh in the 2500-2600 lb range leaving around 2300-2400 lb payload in the bed.
Lots of newbys get taken in by those high or low gvwr based tire placard payload numbers when their figuring how much weight they can safely/legally put in the bed of their truck.
The Titan XD is competing with the F150HD with similar GVWR/GAWRs/GCWR/tow ratings. Both are what they are .........top of the line HD 1/2 ton trucks.
Once 1st/2nd year bugs are worked out the Titan XD will be at the top...JMO.
GVWR has no bearing on the trucks total braking performance.
Minimum braking performance is a function of the vehicle GAWRs.