Here's the calculator I put together with some of my existing gear. Weight of the Ovrlnd is an estimate. Weight of the bikes is estimated high to account for the associated gear and the 60 beers is just the capacity of the cooler. So while some things are estimated and some estimated high, there are defintely small odds and ends not included. The current calculation has me very close to max payload. Obviously, the TRX has the power to move more, but the rear on these things are quite soft and there are currently no solutions in the market as far as stiffer coils or helper springs so my concern is sagging
So, being a Toyota guy, can't help on the TRX vs PXL, but can give you some feedback on the Ovrlnd weight issues: Just weighed my now completed and fully, but fairly lightly built rig last week on the way back from a trip and was a little surprised at how heavy it was. That's largely my fault for being a belt and suspenders guy, mostly due to traveling as a solo rig, and going some difficult places. Too much reco and SHTF gear, extra water, fuel etc.
FWIW, I went with the Ovrlnd specifically to avoid the HD 3/4 ton headaches others are mentioning. Looked at F250s and a FWC, but camper issues aside, didn't like the weight, size and turning issues with the bigger truck. Figured the Tundra (at a 4 ft bigger turning radius than my Tacoma, and 5 ft LESS than a Ram 2500 or Superduty) was the trade off to make, and I'm happy about it.
Truck weighed on CAT scales at bone stock: 5900 lbs with me and wifey (282)
Truck, bone stock with Ovrlnd and 58lbs of some bed prep for build out ; 6320 lbs. Camper weight (unmodded) = 362
After camper build out (detailed on the Ovrlnd only thread, but insulated, electric system and cables, heater, fridge, 100lbs of built ins, 8 gals water), truck mods (34s, sliders, OBA, Alu skids, suspension, HD Deavers, heavy cable fm alternator back to camper, regear, lockers, but NO heavy bumpers, winch etc) and pretty close to fully (over)loaded coming home, except for some food and water: 7680 lbs
My specific payload was rated at 1290, the truck GVWR is 7100. I'm not over my combined axle VWR, but heavier than I'd like or thought I'd be. Took EVERYTHING not fastened down out of the truck, weighed each item and weighed the fully built out, empty rig (again with me and wifey) and it was 7100 lbs on the nose. So I'm gonna pare down some unnecessary stuff and get it down about 200lbs, and I'll be fine with that. I'm gonna guess your camper, once you do the inevitable add-on's and mods will add more weight than you're planning for, BUT I don't really thing these campers need an HD truck as long as we are deliberate about what we bring. Can't speak to your rear coil issues though . . .
With the regear to 4.88s and running Cooper AT3 XLs at 45psi and loaded I got 14.2mpg coming back from our recent trip from Kingman to Phoenix with headwinds at times and up and downs. Regear definitely helped.
This last trip did some very rocky, bouldery, ledgy, sandy, remote tight trails in NV. No problems. There were also three times I'm glad to not have had to manage some turn arounds with a longer wheelbase or longer truck body, with a bigger turning radius. Point being, I didn't need 40's or a larger HD truck to go anywhere I wanted to be or to carry the load. I'm betting you don't either, but that's a personal choice. YMMV.
Not sure about the TRX as it's specialty 1/2 ton. But if you're careful with weight and can augment the rear springs you may well be fine
Hope this helps your decision process a bit . . .