My method is to totally ignore the max towing capacity. It is an advertising gimmick ONLY and not even close to real world. It assumes a bare naked truck, no options except Max Tow, only 2 passengers at 150# each, and absolutely nothing else! Every pound of options, passengers above 300#, and cargo must be deducted from max tow capacity. Read the fine print, and you will find this.
My preferred method is to find the yellow placard on the driver door latch pillar which gives you the "weight of all passengers and cargo shall not exceed XXXX lbs" This is exactly says. AKA Payload. This is specific to THAT truck as it left the factory.
Add up the weight of all passengers, pets, car seats, snacks, tools, firewood, toys and anything else you plan to carry in the truck. Add 80# for a WD hitch. Now subtract this number from the Payload. This is your maximum Hitch wt, which will leave you right at the truck GVWR.
Assuming 10% hitch wt, the absolute max TT weight is 10 X hitch wt. USE CAMPER GVWR IN THIS ESTIMATE!! Nobody camps with an empty camper!
I would prefer to stay at 90% of that weight as most numbers are just estimates.
Other weights like GCWR and rear axle WR come into play, but if you follow this system and have significant weight in the truck, the other weights fall in line.