Dave's input will be in the gameplanning. It is far fetched that he listens in on Edwards' calls and over rules them when he doesn't like them. That just doesn't happen. Do you realize how quickly this would make Edwards/Wannstedt relationship go south? If that happens, you might as well fire Edwards.
During the week, the STAFF as a whole creates the gameplans, what coverages they like when, what blitzes they like vs certain formations, etc. This is all a staff discussion. When it comes to calling the play , there needs to be ONE person who makes the decision. There is no time for indecision on the sidelines. If things go wrong with that one person (Edwards), then he will be canned and most likely Wanny would take that role.