I am thinking about using the multitenancy feature to add new users from a different business. Ideally I would like multitenancy with isolation so that the companies are completely separate and I can create dedicated branding.

I've had Totara for about 3 years have 420 users on the system and currently have v16 - all three products.

If I enable multitenancy, do I need to set up a tenancy and assign the existing users to "Company A" and then set up "Company B" for new users or can I leave all the existing users without a tenancy and just create a single tenancy for the new users?