Meteor CRUD many-to-many relatioships MongoDB

Hi everyone, I have 3 collections interconnected through many-to-many relationships. Therefore, I have 2 concerns:

  1. Should I have 2 arrays with 2 ids in each of the 3 collections, or one join collection with 3 ids?
  2. How to perform reads, inserts, updates and deletes, so everything is in sync and integrity is ensured?

Thanks in advance for any help