I'm not here to answer all your questions, Jeff. I'm still trying to figure out the answer for myself!

If you're using a sandwich wall construction with a 3/4"+ foam interior, then you can get by with shallow junction boxes from the big box stores. Good luck trying to squish all the wires for a middle-of-run outlet in there, though! I tried that, and didn't like it too much ...
I've also tried surface mount wiring and junction boxes, like what's used in garages and basements. You can either use metal conduit or PVC conduit, boxes, etc. If you're retrofitting a trailer, or if you've already built the structure and cabinetry, this is your best bet, probably.
Most RV outlets require a 1-1/2" deep space for installation. Most teardrops don't have that ...
So far my best solution is just to confine all my electrical to the cabinetry and build mini chase walls. Not very flexible, but so far it's my best solution. Any body else have another idea?