Silverfz, slow down and separate wants/ needs/issues. You’re all over the place! Lol
Payload, half ton is a half ton pretty much, the MAX payload half tons are just stiffer springs and maybe harder tires. (Ford used to put a bigger rear axle in, not sure if that’s still the case. Either way you’re not pushing the limits of the axle with what you’re doing)
Nothing more and nothing that can’t easily be upgraded on lower payload rigs, as you’ve already done.
Fuel mileage will not be appreciably better or worse with any new model gasser when towing. IE you’ll still get 8 mpg when your foot is planted and the truck is doing work.
Comforts, features, reliability? That’s all subjective stuff and up to you.
Have fun truck shopping!!