Hi Audrey - welcome to the Cvent family! :)
I'm curious what others in this group would say, but from the Cvent side it's common for agencies to manage multiple clients in one account. Either option works in your scenario above, you could either use 1 generic domain across all events/clients or you could request to add additional domains to your account so you could have specific domains per client. You would just need to work with your Account Team to get those added.
Hope that helps! Let us know if you have any other questions.
------------------------------
Denise Sutter
Channel Marketing Manager
------------------------------