Multi-Tenant Microsoft Exchange Online support

Company I am working for is in the process of migrating our Exchange  on premise clients to Microsoft Exchange online.   We are partnering with Pax8 for licensing portion of it as well as Microsoft technical support.

I want to be able manage all of these tenants through a single interface so we can control access to that select set of accounts so as technicians come and go in our team, we can manage access to that single interface.

Wonder what 'best practice' would be in this scenario.