Seamless Application Access and Lifecycle Management for Multi-tenant Azure AD Organizations

This article positions cross-tenant access in context of single organization with multiple tenants, and all accounts to count as 'member'.

What is the role for setting up (Azure AD) B2B with an external organization? Before when trying via 'New-AzureADMSInvitation' to invite a guest from other O365 cloud, an error was reported on 'National Cloud'. Since a few months that is replaced by error pointing to non-matching cross-tenant. Is Azure Cross-Tenant also (and perhaps even more) intended to provide B2B alternative for current Azure AD B2B process with Azure AD guest accounts? If using cross-tenant with an external organization; how will the synced accounts appear: still as guest, or as member, not distinguishable from the own employees; and e.g. also granted access in SPO sites that have 'Everyone except externals' ?

See also: https://learn.microsoft.com/en-us/azure/active-directory/external-identities/b2b-government-national-clouds