Each conference has a mix of class A, B, C & D schools. The power conference (Conference 1) is the top teams independent of what class they fall under (A, B, C & D) and I believe each conference gets weaker (lower pre-season seeding criteria) as you go down. When the playoffs start the teams all go back to their respective class. Playoffs are not by conference. All the power conference teams get in no matter what and the remaining teams are picked from the other conferences depending on win/loss records and probably pre-season seedings.

In the playoffs, you might see a power conference team with a losing record being seeded higher than a conference 5 team with an unblemished record. On paper this does not look right but in most if not all cases the power conference team will win