There are nine conferences in the FBS, the Power 4 (was Power 5 before the PAC shrunk too small to qualify as a conference)--the SEC, B10, B12, and ACC--and the Group of 5-- American (AAC), Conference USA (CUSA), Mid-American Conference (MAC,), Mountain West (MtnW), and Sun Belt (Sun).
Now here's the key to understanding playoff seeding: the CFP rules treat all nine of those conferences EXACTLY the same. There is no upper tier P4 and lower tier G5. There are just the nine conferences.
I'm not saying the CFP Committee treats them all the same when they rank-order teams each week; they don't, no more than the AP and Coaches Poll. We all understand where the powerful teams are, and they usually get ranked accordingly.
But the CFP rules treat them all identically. Like this:
The four highest-ranking conference champions get into the playoffs, AND get a first-round bye, regardless of where they're ranked. They are seeded 1 through 4, again based on their CFP Committee rankings.
The fifth highest-ranking conference champ is guaranteed into the playoffs. But gets NO guaranteed seeding. If he's ranked among the top 12, he'll get that spot. If he's below #12, he'll get the #12 seed.
~ ~ ~
And that's it. No special treatment for Power 4 conference champs over G5 champs. If the five highest-ranking conference champs were teams from the AAC, CUSA, MAC, MtnW, and SunBelt, those would be the conference champs who were guaranteed spots in the playoff.
That'll never happen because they'll never all be ranked that high, but the rules would allow it if they did.
Simple.
Go Vols!