Shanghai Format

What's this opponent choose a team to face? Anyone care to explain ? How's this format working

After Lev VS Fut ended, there will be a draw but instead it’s for the 1st seeded teams on who’s getting to pick first

For instance, Fnatic get drawn first so they will choose whoever they want to face. Let’s say they pick GenG so other teams (PRX,EDG and 100T) can’t pick geng

This will repeat until everyone has chosen

Are the teams going to pick their opponent at the same time at said draw, or is the actual picking going to be saved for a later date.