1. I don't understand why you would want to do that? If we would have a system like that, you would loose the possibility to do incremental backups as the different jobs won't know anymore what has changed from their last job. There would be parts of data in backup 1 and parts in backup 2... Is there a specific reason why you want that?
2. Are you talking about OU's from Azure AD or on-prem AD (in that case hybrid AD I assume)
3. So you want 1 job to run and when it finishes automatically start the next one?
Let me know