Geez, I had to restore my OS, the Windows user profile got corrupt. Luckily I do a full OS backup once a week so I managed to restore it in just minutes.
I mapped a drive back to my laptop. I then hopped on my server and added a new library using the mapped network drive. I then loaded the Servers dashboard on my laptop and the new library was there. So having libraries on remote network mapping works fine. It is basically the same thing as using network attachments to a NAS. You don't get any advantage in CPU for transcoding doing this because the server is just using the second server as storage. You DO NOT need to install Plex on the second server, as I said it is simply using it as storage.
One thing that may trip you up. When you open the dashboard in a PC at least you have to go to the bottom and click MORE and then locate the new library. Click the three dots menu next to it and tell it to PIN to the dashboard. Other client devices might need the same thing.
Also make sure you can see the media over the share, make sure the NTFS rights are open to the user you are using. If using a share you created also make sure te SHARING rights are open. If you are using the hidden $ shares the sharing is already there. Just make sure the user you are using has the proper rights or belongs to the administrator group.