RHEL 7.6 add domain users to local group and UID mapping

Hello,
I configured AD domain logon on RHEL 7.6 server by relamd and have two questions:

first how when domain user logon first time (allowed from 'example@domain' group) how to automaticaly add that domain user to 'test' local group?

second question we will have plan to migrate ca. 1000 local users from one server (old debian) to rhel 7.6 'domain users'. Our policy was that local users have the same login as domain user (except @domain part). I can get list user names and UID's for each user, I can transfer home directories from old /home/user to new /home/user@domain. But how to get new domain user automaticaly access to their new /home/user@domain directory before they login first time new server?

thank you in advance for help

Maciek