I agree, I went from a 1500 bighorn, to my current 3500 DRW HO, primarily because the cummins in the 2500 gave me basically the same payload as my 1500.
pin weight is easy math:
Payload rating minus passengers, cargo, and accessories on truck = remaining payload.
Max Trailer weight = remaining payload x 4
you cannot use pin weight sticker unless you pull your trailer empty...
some fifthwheels are biased at only 16% Pin weight, mostly "150 series" or half-ton towables.
Quick examples of why I got my DRW.
previous truck:
2020 1500: Payload 1768, passengers: 560lbs for my family of 5, dog 70lbs, extra equipment and cargo 150lbs.
remaining: 988 lbs
Planned on Reese goose box to reduce hitch weight, but that leaves me with a 3900lb (6175 @ 16%) fifthwheel capability
2500 we liked:
2020 bighorn cummins: payload 1910,
passengers: 560lbs for my family of 5, dog 70lbs, extra equipment and cargo 150lbs.
remaining: 1130 lbs
Planned on Reese goose box still to reduce hitch weight, but that leaves me with a 4520lb (7062 @ 16%) fifthwheel capability
3500 DRW we have now
2019 tradesman cummins HO: payload 5822,
passengers: 560lbs for my family of 5, dog 70lbs, extra equipment and cargo 150lbs, aux tank + toolbox 1100lbs, 250lb hitch
remaining: 3692lbs
Planned on Reese goose box still to reduce hitch weight, but that leaves me with a 14768lb (23075 @ 16%) fifthwheel capability
our RV
KZ Durango Half-Ton D286BHD
Max pin weight:2625lbs
Max pin bias: 25%
GVWR: 10500lbs
dry weight: 8540
dry pin weight: 1570
dry pin bias: 18%
now, all of that said, if you have a 6.4 HEMI you have much more payload and can have more pin weight, or if you have less people and stuff in the truck.
I personally was fine with a bit over payload since i calculated the rear axle weights, but that was for around town and short rv trips, I would not want to tow cross country over weight on anything.