Question on identifying CRMA

My understanding is that CRMA applies to assets that do not have a physical or logical separation of CUI and non-CUI. So, wireless access points that block access to CUI systems are an example of a CRMA asset.

My question is this: If I create a dedicated site in SharePoint (GCC High) that is logically protected via policy and access controls to prevent CUI access, is that site a CRMA asset? Other sites in my SharePoint system have CUI, but the sites would be logically separated.

And if it's not CRMA, can I extend limited guest access to vetted domains to access this site?

My use-case is that I have non-CUI commercial data that I need to share with non-DoD customers, and I want to avoid standing up a separate MS365 account requiring new identities for my users.