Boise State has one decent win and a quality loss (Oregon). That's it.
If BYU wins out, they'll have beaten SMU, Kansas State, Arizona State and Colorado (Big 12 Championship). 3 of those 4 should finish ranked in the CFP.
BYU and BSU would each be 12-1 with conference championships. There is no way that BYU would be behind the Broncos.
Just win out and everything will be fine.