Wavy as it may be a generator cannot help but put out its best effort for a sine wave. It is far and away more important to have and maintain the motor in good working order so the engine does not cough, spit, surge up or down or get feminine-like hot flashes.
Always start the biggest load first the successive smaller loads. The generator certainly will run the converter, a coffemaker and a microwave oven at the same time. One RV battery can take a 30-40 amp charge rate and a pair of them 60-80 amps so cutting down on generator run-time when boondocking means increasing the battery recharging potential by a bunch. When any of my generators start up they have a list of chores to do - no slacking off with $3.50 gallon fuel.
Generators require maintenance. Which includes cleaning and oiling the governor linkage. Learn how.