First of all, the main difference between the two is that CFE is currently supported and under active development while AMP has been abandoned. QCar is the only other active Mac FE at this time. Even still, hopefully i've answered your questions below.
To the best of my knowledge, there are no plugins (besides the iTunes controller that comes with it) publicly available at this time. A couple of people have talked about making some, but as yet nothing has come out. I've been focused on the App itself, so I haven't had time to work on any either.1. Where would I be able to aquire the plugins that have been developed for CFE thus far?
That is the big one. The other is the basic architecture. I liked the look of feel of AMP, but adding new features was a very painful process. I also didn't like how everything was built into AMP as it meant there was more installed than I wanted (I believe in a minimalist approach to application design).2. What are the differences between AMP and CFE? I see that AMP is no longer being developed.
I would say QCar is the most promising in this regard. They still don't have Nav finished yet, but from what Jirka has shown us so far it is the only one that is truly integrated with a FE that makes it easy to use.5. Is there any GOOD mac native app for navigation. The best in my limited searching seems to be RouteBuddy, and that one appears to be sadly lacking in interface and esthetics. Also, what hardware works the best with this?
Poke around the LCD and worklogs forums. 10" and 12" LCDs are not uncommon and I believe one person has a 15" IIRC.8. I have a 350z with a GIANT area of console to slice and dice for a screen. Does anyone know of or have experience with larger touchscreens than 7-8"? What is the largest you know of?