Say all the Coaches I have on D run a 4/3 scheme and one is hired but runs say a 3/4 along those lines. How does this effect the overall scope of the D?
Is there a hidden penalty somewhere because of different philosophies? Does it matter?

Each team has 12 coaches: a head coach, two coordinators, and nine position coaches. Coaches are important in the development of your players, and your head coach also determines your team's playbook.
If you click on a coach, you will see his detail card. Here you can view his ability to improve various skills of the players under his watch. As a player's progress is calculated, his head coach influences his attributes by 50%, his coordinator influences his attributes by 30%, and his position coach influences his attributes by 20%. The higher the influence, the faster his current value will approach his future value for that attribute. Attributes that do not apply to the player's position will slowly decline.