The actual brake disc area of a DRW of same year model is just marginally larger than that of a SWR, and actually locking the rear brakes on either is nearly impossible when under load. If you could actually lock the rear wheels on both then the extra braking goes to the DRW.
In the OP scenario.....nothing short of a class 6 or larger would significantly shorten the braking distance. Anyone relying on the tow vehicle to stop a heavy load are pretty badly mistaken.......the trailer brakes should be the primary stopping component for the trailer! Anyone doubting this, just hook up to about 20K pounds, do not connect the wiring harness and do a panic stop from about 60 mph. I think you’ll gain a healthy respect for the benefits of good trailer braking and the inability of a pickup truck to quickly stop said load! memtb