I had a 2004 Tundra 4x4/2004 Hawk for a few years and added helper springs to level out the ride. The biggest issue I had was braking was marginal. In 2015 I bought a new Tundra 4X4 Double cab and had 2 different fairly loaded Hawks on it. I added Ride-Rites to raise the rear a couple of inches. I never felt the need to do any other suspension mods, but never liked the ride with the camper off. The rear end was lifted an inch or two with the Ride-Rites at 15 psi and it made the rear end too bouncy. I now have a 2019 Tundra 4X4 Double Cab with an ATC Panther Shell equipped with side dinette and stove. The factory weight is 900 lbs. Being a backpacker I'm pretty minimalist in how much stuff I need to bring on my trips. I've had this combo for a year now and haven't felt the need to do any suspension mods though I suspect if I had the camper on full time I'd probably add Sumo Springs in the rear. I live in the foothills and daily driving consists of hills and lots of curvy backroads. When I'm out wandering it's generally paved roads until I hit the backcountry and then it's mainly gravel roads and nothing too crazy as I'm still running the Michelins that came with my Tundra.
Good luck sorting it out!!