If you look at the portraits of the people you recruit from in villages it will say if they are infuential, powerful etc. If they are powerful you can recruit nobles from them.
Imo the only clearly best unit is Battanian fian champions as archers and Khan's guard as horse archers. Cavalry you can make a case for both elite cataphract and banner knights
Infantry is currently kinda **** no matter the tier, they are only there to protect the archers. Don't invest too much time getting an elite infantry section, they won't win you the battle