Hi @nolanl13,
The use of Organizations really comes down to your specific use case and your/your customers requirements, so there is not always a clear cut answer for this and needs some thought.
We do have plenty of information available to help you evaluate and decide on the best approach to take, I recommend you start by taking a look at our Architecture Scenarios, specifically the B2B use case.
You should then take a look at Multiple Organization Architecture, where you will find some example use cases and further details.
Since you want to have a single user (team member) to be able to be apart of multiple organizations it would make a lot of sense to use a single tenant and to use the Orgs feature. It would become quite complex if you wanted to have businesses on separate tenants and attempt to sync a user between tenants.
I hope the information above helps you find a decision that right for you!
Thanks