A. Two vCPUs with one core
B. One vCPU with two cores
>Does the amount of hosts and virtual machines matter?
Yes, for the size of the database and (at some point) for vCenter performance - tho the bigger impact will be on the SQL server.
And 2/15 is no where near where that would be an issue. Maybe 200/1500, depending on logging level, # of admins etc etc
>Are there any other supported configurations and how are they determined?
Probably the CoE (Center of Excellence) has a guide for that, but in the real world start with two and add more later if you see high CPU usage.