The "Plex Media Player" is not only a simple Player: with the support for a variety of formats and other useful features, it is the perfect complement to your Plex Media Server.
The CHIP editorial says:
The "Plex Media Player" is now available for free for macOS and adds some useful features to your "Plex Media Server&.Plex Media Player for macOS Since 2015, the "Plex Media Player" exists as a supplement to the "Plex Media Server" - but only for holders of the paid subscription. Now the software is also freely available for free users.
Plex Media Player: free Player for the Plex Media Server
If your server is already set up, you can get started right away - in the confident library view, you can quickly select videos or music or browse through the search. The Player plays all common formats and uses the open source format MPV. You can use your tablet or smartphone as a remote control and also save videos online for later viewing. remote access to the server is through an encrypted connection.