Hi Kevin S. This can easily be done in Salesforce, and I've seen it set up a few different ways. First, as everyone has mentioned, gauge how supportive the SF admin/team will be. If you have a good connection with tech ops, this is not a huge lift.
Within the contact record, customers can be designated as CAB member, advocate, etc. with a simple drop-down field, plus an open text box for historical notes related to those activities. I would add a date field for when the advocate was last touched to teack the need for revalidation.
One option is to use Tasks, where you can add multiple Task types such as recruiting, requests, case study development, etc. Within those Task types, you can add steps for process workflows.
You can make these fields visible by permissions so if you don't want a certain group to see your notes, that is possible.
As for a threshold, I'd say once you get to 500 records in a spreadsheet, it's time to automate in some way. Ideally, a customer platform will have more functionality and in the long run will make your life easier, but you'll also need someone to own/admin/ and keep that updated as well.
I've attached a pin you can wear around the office to start building that relationship! 😄