I know that the top 4 from each division make the A playoffs, but how are those 8 teams seeded? Is it 1-4 in National and 1-4 in American and 1 in National plays 4 in American or does it stay within the divisions until the championship game?

top bracket

1N vs 4A
3N vs 2A

bottom

1A vs 4N
3A vs 2N

So if seedings hold, 1A would have to beat 4N, 2N and then 1N to win the championship (and vice versa).