I have found that onboard generators are louder than a portable honda generator. With the honda (or other quiet inverter generators), you can angle it away from your neighbors. Onboard generators point where they point.
I have seen no difference between onboard generators in trailers vs. motorhomes. They are the same generators with the same default "point where they point".
If the campground does not have stated generator hours, then to my mind one should be reasonable in its use:
If the weather requires AC overnight, then it would be acceptable to do so. If the RV is simply a bit "stuffy", then open windows and use a fan - not the AC. Don't run it so you can watch midnight movies, etc. Only use it for necessities (medical needs, etc.).
Don't start the generator after 10 pm or before 8 am. If it's already started and kept running, that will be less impactful on your neighbors than if you start it up after they are sleeping.
If your neighbors are in tents, then be more conservative with nightime use (unless they are using their own generators during the night).
If in doubt, ask your neighbors if it is bothering them.