@EspenB89 No, Plex would not hold the password for your Google account, they would pass authentication over to Google and Google would confirm it and pass confirmation back to Plex as part of the SSO process.
The hackers would, however, have gotten hold of your Google email address as this would be associated with your Plex.tv account. So, I do not think you should be concerned with your password (encrypted or otherwise) being taken in the breach.
I would personally not be inclined to use 3rd-party authentication to log into any service and use a unique email/password combo for each service I use, as this prevents any chain-reaction after a data breach such as this.
Not shilling, but something like SimpleLogin can assist here.
