From what I have read here and elsewhere, be sure to include in your research a new to US market one from Truma. I found one of the persons who tested this unit and he swears by it. So, I am about to buy one. Just waiting to find a near-by dealer to sign up so I can get it installed.
http://www.truma.net/us/en/press-events/truma-aqua-go.php
https://www.youtube.com/watch?v=OUjoK0WgsGQ
Based on what I have heard about pricing, they may be the most expensive ($1199.00 for the middle model). However, they claim not to have the temp fluctuations associated with flow issues that all the others have. I cannot comment yet on any personal experience...
As far as your other questions, I have read that the ones for a home do not work in RVs, and the electric versions draw way too much amperage to be feasible in most trailers. So, all of them, including the Truma one, run off of propane. You may get more informed posters to respond more comprehensively to your questions than I can.