If Miami wins out, it will win the AFC East, even if New England wins out.
If they both win out, Miami and New England would both be 11-5. They split their head-to-head match-ups, which is the first tiebreaker. They would both be 4-2 in division, which is the second tiebreaker. They would both be 9-2 in common games, which is the third tiebreaker. But Miami would be 8-4 in conference, and New England would be 7-5, which is the fourth and potentially decisive tiebreaker.