Makeups/delays/suspensions/etc. are all handled by MLB Rule 7.02.
MLB Rules 2018: http://mlb.mlb.com/documents/0/8/0/268272080/2018_Official_Baseball_Rules.pdf
7.02 starts on page 85.
7.02(b)(5) is the rule that dictates if games have to be played or if you can finish the season with less than 162 games played.
Any postponed game, suspended game (that has not pro- gressed far enough to become a regulation game), or tie game that has not been rescheduled and completed prior to the last scheduled game between the two teams dur- ing the championship season must be played (or contin- ued, in the case of a suspended or tie game) to a com- pleted regulation game, if the League President deter- mines that not playing such game might affect eligibility for the post-season and/or home-field advantage for any Wild Card or Division Series game.
I think this means the only time it wouldn’t be played that could affect playoff seeding is between Division Winner 1 and Division Winner 2 since they both already have home field in the LDS.