On the startup tab in the Windows Task Manager, in addition to make sure launcher.exe isn't there (or is at least disabled), make sure browser_assistant.exe is disabled.
Sort-of found a fix, resetting the passphrase and sync did not do anything, it was still displaying the wrong one all the time so uninstalled and reinstalled but now it is syncing and not asking for a passphrase, my normal opera log-in seems to be all that is required.