Once you invite a person to collaborate with on any of your Stories, this allows them to see that specific Story and its contents, and the Collaborator can add new content. You, as the original creator of the Story have the ability to continue to add new Collaborators and you can remove a Collaborator at any time.

Yes, you can collaborate with any number of people.

By selecting “sharing”, within the Vault itself, you can add the email addresses of those individuals that you want to collaborate with on that Vault itself. As the owner of the Vault, you can cancel or rescind their ability to collaborate on that Vault at any time.

No, a collaborator ONLY sees the contents within the Vault that you have allowed them to collaborate on. They do not see any other Vaults or account details.