The B1G and SEC are so dominant in the polls that they'd likely take those 4 spots.

Right now the 4 home teams (#5-#8) are

AP #3 Penn St
AP #4 Ohio St
AP #6 Texas
AP #7 Tennessee

Notre Dame would also be ahead of us for an at-large spot (presuming CFP rankings are similar to AP, no guarantee there).

Some might lose, but if we take a loss we'd have to worry about being passed by Texas A&M, Clemson, Indiana, Alabama, Boise St, Pitt as well as a few Big 12 teams. We wouldn't drop behind all of those and some others would also lose, but home field would be tough.

My thought is

Win the conference title (undefeated): Likely #4 seed, possibly #2 or #3

Lose the conference title after going undefeated in regular season: Definitely in the CFP, on the edge (but probably short) for home field in the first round

Lose a regular season game AND the conference title: Real chance we miss out altogether, but end up kind of on the bubble.

Lose 2+ regular season games AND the conference title: Well it was a fun season while it lasted and we'll still get a good bowl game, but CFP isn't happening