Strategy for collaborating with customers (i.e. guests)?

We have a few thousand customers, who we engage with on a regular basis, historically via email.

I would instead like to use a platform like Teams. Does anyone have any suggestions on how they would do this?

I was thinking:

• One team per customer.
• The General channel is used for everyday communications between us and the customer.
• And a private channel for all internal communications which we don't want the customer to see.

But then I have some other questions like:

• How can I create these customer Teams / Channels that all have the same Team settings, channel permissions, and folder structures?
• Are there any potential (security) issues with my above strategy, with the customer accessing info which they shouldn't? e.g. Weaknesses between the public and private channels?
• Are there any maximum count limitations I need to be aware of, such as Team, Channels, Users?

Thanks or any input.