The general consensus is that when you get a difficult match in youth football you get trouble from the sidelines, in adult football you get it from on the pitch.
Once you've got some experience under your belt and are comfortable using your cards, the tools for dealing with problem players are simple and straightforward to use - while the decision of if/when to confront a difficult manager is much less well-defined. But on the other hand, trouble from off the pitch leaves you with only the two managers to deal with, while difficult players might be easier to deal with individually, but the trouble could theoretically be coming from 22 players at the same time.
I think starting in youth and working your way up is generally good advice to be honest, especially for someone who's going to be as young or younger than many of the OA players. Which you'll end up focusing on long term however is something you'll only find out with experience.