At the start of the game you obviously have the opportunity to decide upon the size of the database. I always customize it as it opens up the game as the save progresses. Once you're ten seasons in, it's great to have a bit of diversity to the regens coming through.
This could depend on who is doing the recommendation. If you're scout has 12 for PA and CA but the coach who is rating the player (when he's your player) has 5 for PA and CA then his ability to judge how good the player is is flawed. It's always a good idea to have a member of your coaching staff to have as strong PA and CA attributes regardless of their coaching ability in order to give accurate reports on your own players.
This will be it, a coach will rate the player when he is at your club