Just like your truck questions, seems like you’re totally on track, with the right considerations being made/asked.
Second on the water tanks. Although unless you’re living like hippies or taking sponge baths, if you’re spending more than maybe a week boondocking, water will become scarce. However, you’re not going to find a smaller lighter rig that packs hundreds of gallons of water, so maximize what you can get in tank size and then have a water hauling plan if you’re off grid for longer than the water lasts. IMO, the whole point of ditching the tents and going to a camper is to have amenities and water/showers is high on most people’s primary amentities list.
(Fwiw when we need to pack in extra water, I use one of my wakeboard boat’s ballast sacks. Fits easily on the floor in the back seat or in the truck bed, hauls an extra 50gal)
The other thing not mentioned yet is trailer cargo/axle capacity. Especially, if f/t you may be packed heavier than average. Some /many TTs don’t have a lot of headroom with spring and axle capacity. This would be a primary concern to vet out, as you’ll want reliability and many miles of service as full timers .
