Disc Brake Question

Calipers can go to either the front or the rear. Only difference is hose routing and maybe some interference with the anti-sway bar depending on what year and model you're messing with. No change in performance. Not sure what efficiency is but whatever it is it doesn't change either.

There are some calipers that can't be rear hung due to their design. Best ones to rear hang are the ones that are designed to be rear hung such as the late model FMJ units.

It is easy to get custom hoses built so don't bother trying to use some dumb looking factory hose that loops all over the place. Just measure out what you need and go to a place that can build custom brake hoses for you. Lots of shops have the ability these days.