You will bake.
It's not just the external temperature but also the internal temperature rise in the trailer during the day and the cool down (or not) time when you return to your trailer in the evening.
Depending on the Air Conditioner, it may struggle anyway during the day and evening.
Buy the bubble silvered sheets and cut out to fit in any skylights and windows. Also consider window awnings.
Moab KOA is well placed to explore the town although there are many other good sites as well. Passport America works well too and its well worth buying the subscription for the deals. If you stay in KOA's, buy their subscription and also buy the Good Sam subscription. I own all three. You will save 10% with the last two on your camping stays.
My advice is to pay the price and plug in at an electric site and also follow the above advice anyway.
"Want QUALITY. No de-lamination, roof leaks, thing breaking in general."
In my view Artic Fox are hard to beat in the box type trailers. Been RV'ing now since 2001 and have seen a lot of older ones in excellent condition.
On the other hand, if you can loose the new and slide out requirements, used Airstreams are hard to look past. :D
If I had bought an Airstream from the get go, I would probably have stayed with the brand and trailers rather than go through 4 previous RV's.
Also consider solar windows 15k air and window awnings for those hot summers.
Owned Sunline and Mountaineer Trailers plus Dolphin and Allegro Bus MH's