I'd love to have McCaffrey, but I don't think that's a good long-term move. You don't need an elite RB to win a SB. You need to prioritize QB, receivers, and defense. Running game just needs to be respectable.
McCaffrey is one of the best pass-catching RBs. He can run in the Bills scheme. I'm not for taking on that contract, but it's not like they would need to adjust much. He would be used the same way as their current duo, but solo.