I'll use 15A to run the AC long enough to cool the unit down if I'm in and out before or after a trip loading / cleaning. If I did it often or for very long, I'd put in 30A. I've never had a problem and the AC draws well under 15A while it's running. I won't use ANYTHING aside from an LED fixture when I'm doing it though. Now, when I'm not running the AC, I'm not afraid to run nearly everything else in the trailer off of 15A...microwave and water heater on electric will trip it if they run at the same time, but everything else is fine. I wouldn't try to run a coffee maker or hairdryer off the trailer plugs like that though. That should give you an idea of what you can run on a 15A circuit.
2012 Chevy Tahoe LTZ - HD tow package
2017 Rockwood 2703WS Emerald Edition