The Axis and Vegas are identical in floorplan with only minor cosmetic differences (color scheme, headlight orientations, etc.).
We've used our Axis to tailgate my son's baseball games:
Quality wise they are probably slightly above average for Thor. There are many happy owners but there is the unlucky one with some serious issues. You really need to have a good dealer to sort that out.
As far as TX heat: yes get the larger A/C unit but also get front window shades (like the Magne Shade unit
or a Sunguard RV Windshield cover
) they will drastically reduce the amount of heat coming in from the front window.
The frame is an E-350 or E-450 (depending on the floorplan you get) with the V-10 engine. There is more than enough engine for just about anything you want to tow (the V-10 is also in the much larger F-53 framed motorhomes thus there is plenty to spare in a smaller unit like the Axis/Vegas).
Genny runs off the gas tank.
Lastly, if you're even thinking of an Axis or Vegas unit download and read the crowd sourced user manual here: http://www.thorforums.com/forums/f10...nual-4961.html
(Pretty much all of your questions and more will be answered in that manual.)