OSU is the best team in the country until someone beats them.
Indiana might be the best team in the country but there's no way to know until they play OSU.
Navy hasn't played anyone yet, but we're going to find out who they are soon - they have a stretch coming up of @ #12 Notre Dame then vs. #18 USF then @ Memphis then their rivalry game against Army. If they run the table they deserve a spot in the CFP. Navy vs. USF may determine which gets that Group of Five spot in the CFP.
GA Tech hasn't played anyone good and their schedule is so weak. They're probably frauds. We'll find out last week of the season against UGA.
Texas A&M's remaining schedule isn't that bad so it's not inconceivable they could end up undefeated. But they also had a lucky schedule draw this year - no Alabama, UGA, Ole Miss, Oklahoma, or Tennessee on the schedule. Instead they get Texas and LSU in those programs' down years.
BYU hasn't played a top tier team. The Utes are at best "good." BYU still has @ #14 Texas Tech and @ #21 Cincinnati coming up so let's see how they do.