I do my best to stay at a campground with power available. Otherwise how much of the rv are you planning to power? Everything (AC, Microwave, Fridge, water heater, etc) if so start at 4kw and go up. Judicious use of AC and microwave, meaning not at same time, most 3kw. No AC or microwave 1-2kw. Lights only 1kw.
Then you can get into brands, Honda, Yamaha, etc. How noisy do you want it to be? Inverter models are generally quieter and more fuel efficient. Non-inverter are noisy.
For the maiden voyage stay where you can hook up until you figure out the trailer and what you need to run.
My 2 cents worth.
Clif and Millie
Ozzie (half a dog tall & 2 dogs long)
2009 Ford Lariat F350 SRW CC Diesel
2013 Cruiser CF305SK Patriot Edition