Cargo Trailers Yes?/No? Off High Clearance? One axle?/Two?

Tandem Axle. They generally don't need rear stabilizers to keep them from tipping when you go in/out to load/unload when not hooked up to the truck.

The general rule for stable towing, and ease of backing up (for enclosed cargo trailers) is the length should be double or more the width... like 7x14 or 7x16 and up.
7x12, not so good.

6' wide is going to be a PITA though because you can't see it in the truck mirrors behind the camper.
Truck camper, I recommend minimum 7' wide