This is why they put Mateo higher than any other pitcher not named Wheeler. They think he can be a #3 type starter due to his 2 plus pitches and his excellent control. Many times if a guy has 2 plus pitches and excellent control they feel all he needs is an average third offering to make him a legitimate top of the rotation guy. If he does not get there they see Mateo as a shut down closer.
As for the other guys.
Montero they think can be a 3 type guy as well mostly due to his excellent command and feel for pitching and they think he can continue to improve as he is a guy that in two years has come a long way already, so he can get better in scouts eyes. Obviously they think he has the floor of a reliever as well.
On Fulmer scouts worry about his delivery and body and think long term he is a pen arm for now, but the Mets will continue to develop him as a starter.
On Tapia they feel that he needs to improve his slider and other secondaries or else he will be just a pen arm even if his fastball is the best in the system.
As for Familia they think his 2 top pitches are enough to make him a late inning reliever in the majors.