Dont buy anything yet. You have to think about each step you are taking so you dont waste a lot of money. You may need to rethink some of what you are doing. The biggest long duration draw that you will have is the ac. If you are boondocking and moving around then maybe you can move with the weather and try to not use the ac or use it just a little. If you do want to run the ac a generator is an expensive way to do it.
Have you been out west? Many people do the desert in the winter and mountains in the summer. You have limited cargo capacity and limited roof area. Overall I'd take a closer look at your energy management plan and strongly consider solar. When boondocking often times people will try to use minimal power and solar charging.
The lightest weight quietest generator will be an inverter type like the Honda 2000 etc. Your ac unit may run on the 2000 but you would most likely need a micro air start kit at about $300 iirc.
