I know what I want to do based on the package that is coming out. It is not all about on-the-fly adjustements. It is about creating a scheme that you want to run.
For example I might see a certain offensive package and want to call a zone blitz. I already know what changes I have to make to a play to create "my" zone blitz. As the offensive is walking up to the line I'm making changes to my play, changing player assignments.
Adjusting on-the-fly to the formation, you have time to basically shift your LBs, shift your dline, stunt the dline, and maybe shade the coverage one way. That is done after they show their formation.
So I can still do about 4 on-the-fly adjustments very quickly, and change a couple player assignments as the offense is walking up. Yes you have to be very quick sometimes, and you definitely have to plan out a system of what guy you change first, how many times you hit A to get to the next guy, etc.
Sometimes I'm overly ambitious and have to scale back things. But it was extremely fun to be able to go into practice mode and create new plays, then bring them out to the field.