THE ANSWER
Choose Campaign for the story, Horde Siege for cooperative PvE objectives across a twelve-player match, or Versus for four-versus-four competition.
Different formats, different commitments
In Horde Siege, three four-person squads operate on the same map with their own missions. The publisher also describes optional objectives. Versus brings competitive teams into maps designed for the revised movement system.
A match’s total player count does not tell you its party limit or whether your group can reserve every slot.
Agree what a good session looks like
Kingy preparation advice · not a tested gameplay procedure
For a story session, agree how much exploring the group wants. For cooperative survival, agree how you will communicate and regroup. For competitive play, decide whether everyone wants to learn together or prioritize winning.
Do not use a mode’s description as a promise of a particular session length. Match durations and retail queue behavior remain untested here.