Your not kidding about crazy hot. I live in Georgia too. What I have done with my last two trailers is insist on 15000 btu units. The Hybrid I bought had a 13500 and I had them change it over. Makes a huge difference. If the trailer you are looking at has the Coleman Mach with the chill grill you should be fine with the AC upgrade. My new trailer is a 30 ft. with a dometic 15000 AC. It is ducted but it also has vents on the bottom of the AC grill that allows me to dump cold air directly into the trailer. I do that and get things nice and cold and then switch to the ducted vents. keeps thing s nice and cold. In answer to your question about noise. They are all loud. But you get used to it. We have a machine we use to make the sound when we camp without the AC running. White noise can be very soothing.
Retired Fire Dept Battalion Chief
2016 Ever-Lite 232RBS
2012 F150 FX4 W/Max tow & Ecoboost
Getting old ain't for wimps!!!