I'm not sure if it would be good or bad, but iw as hoping to put a 4-blade prop on the Mustang for that real-thing look since every real P51 I know of had a 4-blade prop.
although scale in the fact that it has 4 blades, it will be substantially smaller then the real one, and also the performance will suffer quite a bit with a 4 blade on compared to 2. (real p51's would probably have had 2 bladed props if they could have gotten clearance!, and actually on that same subject I just watched a show on the corsair. apparently the entire driving force behind the gullwing was that they had a monsterous 2000+hp engine in the front, and needed a huge prop, but couldn't get the clearance. hence the wing...)
as far as trainers, almost all the trainers with the exception of the nextstar are basically identical. they all fly about the same, they all look about the same and are constructed almost identically. one thing you will want to watch out for is what brand of radios the instructors have, so you can make sure to get something compatible for trainer box use.