Towability off-road will depend on make. Look for adequate clearance between the axles and frame.
My Weekend Warrior was 41' and 11,000 pounds empty. It towed great on gravel. It was a triple-axle which probably helped smooth the ride. I towed many miles on washboarded gravel roads at near-highway speeds.
Mine towed great empty, except it had a super-high tongue weight. Some of the larger toy haulers could overload the rear tires on your truck because of this.
Must haves for me: Fiberglass front cap.... Anything else gets ripped up by the gravel. Diamond-plate might be ok too.
I will never buy another aluminum-sided trailer. Tree branches dent it up really easy, and I have had a couple holes poked from sharp branches.
Be sure the trailers you are looking at have fully enclosed and heated tanks. Really, for remote boon docking i highly recommend Dessert Fox. They are built-well, designed for off-road travel, and are well insulated.