It's not a duplicate Machine SID issue. The output you provided is completely normal and expected. You ran the command whoami /user, which returns the Security Identifier (SID) of the currently logged-in user account, not the computer itself. Since you are logging into all three servers with the same domain administrative account (oneteco\w919857), the SID will naturally be identical on every single machine in your domain (S-1-5-21-...-9341). This confirms that your user identity is consistent, but it tells us nothing about the unique identity of the servers.
To see the actual Machine SID, you need to query the SID of a local user account (like the local Administrator), because local accounts are generated using the computer's specific Machine SID as a prefix. Please run the following command on all three nodes (PWGIRSQL1, PWGIRSQL2, and PWGIRSQL3) to see the true difference:
wmic useraccount where "name='Administrator' and localaccount=true" get name,sid
Or using PowerShell: Get-LocalUser -Name Administrator | Select-Object Name, SID
What to Expect:
PWGIRSQL1: Will have a unique SID ending.
PWGIRSQL3: Will have a specific SID (likely the "old" SID from the original clone source).
PWGIRSQL2: Because you successfully ran Sysprep, this machine should now have a completely new, unique SID that is different from both Node 1 and Node 3.
If the SIDs from the command above are different (specifically the long alphanumeric string), you are safe. The "duplicate SID" conflict that caused your original issue was between the old state of PWGIRSQL2 and PWGIRSQL3. Since you Sysprepped PWGIRSQL2, that conflict is resolved. You can proceed with the plan to configure the IP, join the domain, and add Node 2 back to the cluster.
VP