This selection essentially amounts to letting CA know which of your Appointment Types should entail a Zoom Meeting:
The two other settings, “Enable clients to join before me” and “Start meeting with video enabled”, mirror the usual Zoom Meeting settings.
(Note also that here, at the bottom, is where you can disconnect CA from your Zoom account, should you ever wish to.)
Here’s what scheduling an appointment looks like for an Appointment Type whose Zoom meeting preference is set to “Always”:
When your clients schedule with you, they’ll never see controls related to Zoom. Instead, the system will automatically create those meetings for Appointment Types that are set to either “Always” or “Usually” have Zoom Meetings.