Games maybe, but i don't think either team changes much at all in their gameplan whoever starts at QB.
Durant and KJs skill set are very similar, the only real differences being KJ has a little more zip on his throws and Durant is a bit more patient with his reads and is good at throwing it safely away when there's nothing downfield and he's under pressure.
Edmonton's offense doesn't change at all between Nicholls and Reilly. The only real difference is Reilly's confidence/experience and his threat to run. But they're both tall dudes with good arms.
Now if Pat White started THEN it would make a big difference in preparation.
As for Reilly's foot, sounds like a similar deal to what Durant suffered in 2011, and played 3 or 4 games on it (which was dumb because they had no chance at the playoffs) but in a playoff game I could totally see Reilly playing on that. I mean only the doctors really know how bad it is, but I would not be at all surprised if he started, especially if it's his left (non-push-off when throwing) foot.