I have a small travel trailer with a Samlex Solar PST-2000-12 PST Series Pure Sine Wave Inverter.
I have a 400watt solar set up with 200ah of LiFePO4 batteries.
My trailer is a Rockwood Mini Lite 2104S, with a Coleman / Mach 15000 btu A/C unit ( i dont know the model off the top of my head).
Would something like the Easy Start 364 likely allow me to fire up the A/C from my 2000watt inverter (which has a peak to 3500watt surge).
If so, should I look at the: 115V-only RV A/C (-X20-IP) OR Standard A/C (-X36-UL)
As you found in your research, the EasyStart 364 (ASY-364-X20-IP) is the appropriate model for your 15kBTU Coleman Mach.
It should allow you to start and run your A/C on your 2000W inverter.
Please be advised though that any 15k A/C will consume upwards to 95% of the 2000W steady-state capacity of your inverter, so you have exercise some strict power management in your travel trailer, especially with devices like the battery charger (converter) which can jump in and start drawing upwards to 1000W in bulk (rapid) charge mode.
Most customers have to manually turn their refrigerators and water heaters to propane mode in order to operate their A/C on a 2000W inverter or generator.