Hi @Richard Scott ,
The steps you have outlined look OK, upgrading Orchestrator is pretty straight forward, but you need to make sure you have backups of the following:
Orchestrator database
The Orchestrator database backup can easily be done from the SQL Server Management Studio (SSMS)
Runbooks
The runbooks can easily be exported from the Runbook Designer.
Integration Packs
The Orchestrator core has not changed much so the integration packs of Orchestrator 2012 R2 will work in Orchestrator 2019, just make sure you have a copy of all installed integration packs so you don't get into a situation with runbooks having unknown runbook acitvities.
If you perform in-place upgrades you won't need to reinstall any integration packs, but it's always good to keep a backup of them somewhere.
As for the accounts everything, permissions should remain when performing an in-place upgrade, but since you will uninstall Orchestrator and reinstall it, you will of course need to re-enter the acocunts used for your Orchestrator services, but these accounts should stay in their local admin/other groups on the server.
Another thing is to document which runbooks were running before you stop everything and uninstall Orchestrator, you can also use the Orchestrator Health Checker to get some information of running runbooks.
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Best regards,
Leon