Hello, a bit unclear question here, but you have the external access and guest access in teams. When using guest access you can configure a lot more settings and permissions than with external access (federation) all the way from Azure down the associated hierarchy such as Groups, SharePoint/OneDrive etc. You can also promote guest users in Azure to members or set specific role assignments to guest users etc. There's literally too much to mention. May I suggest that you simply use guest access between your companies and then use PIM for managing specific role assignments.