Obviously, OU could lose and still make the CFP, not so for Texas (probably). A Texas win would help LSU's optics. This is the time of year where "we" start pulling for teams we already beat to do better. The Cincy win over UCF helps Ohio State, for example, if this comes down to the usual beauty pageant thing.
Of course, a P5 that is 13-0 is almost certainly a lock (Clemson), so that is a good approach as well.