I find that on defense, I can pretty much leave that on auto and the results will be pretty good. Only if I'm up against a really good team, will I have to look at playcalling there. Offense is a bit more complicated. With the less skilled defenses, Ask Coach by itself is sufficient.
With the more experienced coaches, you might look at a combination of gameplans, by success, and Ask Coach. I would think building up playcall and strategy with all coaches is a good idea. If you know the plays and how teams relate to them, by play type is a good idea. I generally don't, so I look at Ask Coach.