Most report it will run a 15k AC unless you are in a high elevation ( a free carb jet kit is avail if needed for that) . There is always an option to add a "hard start capacitor" to your AC, making it a much easier task for the generator.
I also looked at the parallel option and almost went that route. I just chalked it up as another extra engine to maintain.
The 3100 should run almost everything, some say both the microwave and AC at the same time even, however, I will stick to shutting down the AC compressor when needing to use the microwave, no biggie
2016 Octane 222-mods already in progress, Husky Centerline TS WDH
2014 Ram 1500 Sport 4x4 QC- 3.92 gears, 32 gal fuel, Zone 6" lift with Bilstein 5100's, OEM brake controller, Cooper STT pro load E 35's, Airlift 1000 airbags, Leer camper topper on the way
2014 Polaris RZR 570 LE-many mods