Plex supports having multiple servers on a single account.
The two Plex servers are independent of each other, even if they are accessing the same media files.
Mount the NAS shares to your Windows system (Map Network Drive). The username/password used to access the NAS must have at least read only rights to the media files.
Then install Plex Media Server on the Windows system, claim the server, and create libraries.
You can leave Plex Media Server running on the WD or not. Up to you.
