How many nodes should a random forest classification have? I'm only using it to determine feature importance nothing more.

Every documentation I can find suggest 3,5,7 or "whatever is proper for your data". Is it based on how many features I have? How many trees I have? How many samples I have? Some mixture?

Overall, 3/5/7 give similar results, but I don't know how to tell if its over or underfitted