Do you also want to be able to access your movies and series outside of your own network? Make sure to leave the 'Remote access' box checked.
Other Plex configuration is based on your needs and situation, just pay attention to language and location setting to better recognise movie metadata and subtitles.Port forwarding is not mandatory required. If you concern about security, no need to enable ‘remote access’ or you can enable ‘remote access’ but not expose the port to Internet directly from your home edge router.map Plex Movie to Synology new created Movie folder, map TV Show to Synology TV folder. In the Plex web configuration page, add media library one by one.Copy some testing movies/music into those folders.
But need to modify the Sharefolder permission to allow read/write for user ‘plex’. You can also use the Synology System Default Sharefolder (video) when use VideoStation or Synology MediaServer.Create Different folders under that Sharefolder, such as Movie, TV Show, Music to manage your media files properly.
I will explain how to make https work later. Otherwise, you will fail to connect through https. If you are using Chrome or Firefox with strict certificate verification, this has to be http not https if you’ve already configured Let’s Encrypted SSL certificate for Synology DSM following this article.
This guide talks about how to install Plex on Synology NAS, configuration and enforce HTTPS on portal.