IF this could potentially damage electronics, are there in line filters that can help here? The price difference is incredible vs honda or onan generators...
The other thing I've found with the Harbor Freight generators is that they're loud. Really loud. Like loud enough that your camping neighbors will hate you shortly after you fire it up. In fact, even you may hate you after using one of them for a while.
I'd recommend a Honda or Yamaha with the appropriate voltage needed for your application. Yes, they're more expensive. Yes, they're a LOT quieter.
I have a Honda 3000 and love it, but I would think the Yamaha would be good as well. You can run the AC and the microwave but not at the same time. Usually not a big deal just flip the AC off for the few minutes you need to run the microwave.
Not familiar with tirewarmers. But if they require 1500 W a Honda or Yamaha will put out close to 3000 W at peak capacity.