I have the 2013 version of your truck and use the firestone air bags with on board pump and remote control to fill and empty bags. I like not having to get a pump out to fill the bags up each time. You will notice on most Fords that you have a vibration when truck is squatted and taking off from a complete stop, with the air bags you can bring it back to level and eliminate that issue. As for one gauge or two I would suggest two, you want the bags to be independent, you don't want to sway or tile and push air into the other bag, they need to be separate.
As for the up-fitter switches I did use one on my 2008 Ford but on the current truck I just went to the battery with in-line fuse, I used the up-fitter switches for other accessories. (front rigid lights, rear rigid lights, in bed LEDs, and high idle mod)
Leon