If two or more teams have the same record in your standings, the tiebreaker by default is:
Higher Points Against
Whichever team had the higher amount of Points For would make it. If still tied, it would come down to which team had the higher amount of Points Against.
Tiebreakers beyond that is a coin toss or can be determined by another metric the commissioner sees fit via custom seeding.
So if you want head-to-head to be the tiebreaker, you can still manually put that team in the playoffs.
If any playoff matchups end with a tie score, the winner is automatically the higher seed.