Definitely go for the inverter generator. It will consume less fuel. The run time is only an estimate - you might well get more.

That Wen is a nice modern state of the art design. My prediction is that 10 yrs. from now, they will be the standard type and the old synchronous gens will be completely obsolete.

A propane generator can run on any size tank, not just 20 lbs. You can get a larger tank or combine two tanks together with a simple hose:

https://www.amazon.com/yianteng-Connection-Splitter-Fireplace-Equipment/dp/B09NR69FP7

Now for $20 you have 11 hours of runtime on two 20lb. tanks. Problem solved!