Client/Brand Lists in Marketing Plus Campaigns

Client/Brand Lists in Marketing Plus Campaigns

My agency is looking at possibly signing up for Zoho Marketing Plus for Agencies but we are trying to figure out the best way to set things up.

From my understanding, you create an account (portal), and then you make a new "brand" for each client within that portal. 

My question today is - within each brand, are you able to import that brand's email lists, etc. completely separate from any other brands you have within your portal? We don't want to have any crossover or strange functionality with these sensitive email lists for our clients. 

If there is, would we then need to look at creating separate portals for each client instead of just having multiple brands within ours?

Thanks in advance!