If there's a tie in a playoff matchup, the higher seeded team will advance. Your League Manager can change this setting by going to the "Edit Playoffs" page.
NOTE: In League Manager Leagues, the League Manager has the ultimate say on which teams advance using the "Edit Playoffs" page. Each league may establish their own tiebreaker system, with the League Manager, advancing the team that wins it. "Most Points from Bench" is an option only available for grandfathered Custom Leagues that used the tiebreaker rule in the past season