Cinicinatti chances of going to a NY6 bowl only go DOWN with a Coastal Carolina win.

Cincinatti only has 2 more games this season, Their most likely situation is to end the season ranked in the top ten. They will have a G5 autobid. and have the ranking to gurantee an at-large bid. BYU jumping them in rankings would mean NOTHING!
BYU vs CCU games has NO impact, as Cincinatti would get both G5 autobid, and qualify for an at-large bid. BYU may win some additional favor in the court of public opinion and steal some Cincy spotlight.

Less likely, Cincinatti has 2 more games, say they lose to Tulsa on 12/12, but still win the conference championship.
If CCU beats BYU, Coastal could easily jump Cincinatti in the #14-#18. Cincinatti would lose their autobid, and CCU would be the lone G5 representative to a NY6. On the otherhand, if BYU beats CCU, Cincinatti could lose to Tulsa on 12/12, drop to #14-#18 in the CFP rankings, and still get the autobid to a NY6 game.

But at the end of the day, Cincinatti is most likely to remain undefeated so none of this matters.