Going to be interesting to see who he wants as a DC. I think he's always had DCs that were 4-3 guys, but he did run a 4-3 hybrid in Dallas. But that could have just been to get Parsons as many pass rushing snaps as possible while not having him try to play the run as much as a traditional 4-3 DE.
Mike Pettine was a disciple of Rex Ryan, and ran a 3-4. He has a preference for aggressive defenses. Even when he's run a 4-3 it's been w/ under principles. Either way, it will be important for him.
He needs an aggressive QB as well I think he and Rattler would be ideal.
As far as offensive schemes, when he took his sabbatical a few years back before getting the Cowboys job, he put effort into learning new schemes new offenses, so he's open to implementing diffrent schemes and isn't stuck to how he does something.