MTO and access to on premises file system

To fix the slow DFS access for users in the remote office, you can:

->  Use Direct Access or Always On VPN to let users connect directly to the on-premises network without going through a central VPN gateway. This should speed things up.

->  Try Azure File Sync to sync your on-premises DFS folders to Azure Files. This way, users can access files faster without needing a VPN, especially on BYOD devices.

->   If you stick with VPN, set up a local VPN gateway in the remote office so traffic doesn’t have to go through a distant gateway.

 To clean up the old unlicensed accounts and make things easier:

->   Use Azure AD Connect to merge the old unlicensed accounts into the new tenant as hybrid accounts. This lets users access DFS with their new licensed account.

->    Instead of using individual accounts for DFS access, create Azure AD Groups and assign permissions to those groups. This reduces the need for duplicate accounts.

->    Hide the old unlicensed accounts from the Global Address List (GAL) so they don’t show up as duplicates in Teams search.