Stick with one axle rather than two if your load allows. Typical axle is 3500# capacity. (Maybe less $ for registration, maybe no inspection requirement - check CA requirement). I still recommend brakes just to take the load off the tow vehicle some. It will be easier to back if it is the same width (or slightly more) as your tow vehicle. I would say less height is better for MPG but your camper should shelter it from the wind load. A rubber torsion suspension will allow a lower load height than traditional leaf springs.
