I believe the team from play-in plays the highest seed possible.
In Pacific Gen G. were in the same group as PRX, so it was shuffled randomly and Gen G. was matched vs DRX.
In EMEA, KC and Fnatic weren't in the same group so the Play-In team (#4) plays the #1 seeded Fnatic.
SEN is coming out of the play-in and EG are the #1 seed. HOWEVER, this could all be coincidence. Sample size of 2 and pacific was weird.