More details giving some examples might get some other responses.
Scripting tools come to mind first, although I am only a user on the domain.
And sometimes combined with Excel.
For example - to loop through all users in an OU and set UserPrincipalNames to a standard format of User@FQDN. Or look for expired logins.
I have limited experience with this. I had 1 OU I was able to manage in which we had external users. I just used VBA in Excel to manage these - global password changes, unlocking accounts, as the users had no access to do this.
Greg E