Can each technician see only their own leads?

Yes: a lead can be assigned to a team member, and operator roles then see only what's assigned or unassigned, depending on the setting chosen. The read-only role can be limited the same way if needed — a partner can consult overall statistics without accessing the numbers, useful for confidentiality in practices. Assignment can be automatic round-robin or manual by drag-and-drop from the queue. Admins, by definition, see everything — that's the price of accountability.