What type of play whether it be pass or run is dependent on many factors. First the score. If we are up by 30 points with the ball and 4:00 on the clock we're going to run. If the score was reversed and we're chasing several scores with little time left we're going to pass. Then, we're going to pass or run based on the opposing D's look. With 8 or 9 on the box we should pass. With 3 or 4 rushing running might be the better call. And they'd much more that figured into a call. This depends on what it is we can do best. If Our run blocking is strong enough to open up gaping holes then why not run? If our OL is better at pass blocking with all our good receivers then maybe passing is a good idea. Then, there's down and distance to consider. This is an obvious factor. The playbook is different on second and one than third and 8. Not that you couldn't run either, but it does factor into the play. There's also the flow of the game. The best teams run multiple plays out of the same set so that the D can't guess the play. McVay has a huge amount of plays in the 11 personnel group and now we see he has 12 personnel plays too.