¶ For every Plex client out of the box, Plex sets the video quality at 720p. Which is good because it will work on the vast majority of existing devices across the board without issue. However taking a 1080p HD video and shrinking it down or in Plex's case… transcoding it down to 720p. What is Transcoding? Great question, Transcoding is Plex's secret sauce. It makes sure that whatever the device you are on, it will transcode the tiny bits that make up a video into a format that your client can understand and display. This is true for both video and audio formats. Why is Transcoding not preferred? Another great question. Transcoding effects picture quality while also taking adverse effects on the server that is sending the digital bits. It has to shrink the bits and then send them to your client. Imagine if it didn't have to change the bits? It just sent them. What's in it for me? Quicker loading times, you press play and the video will start sooner than if the server had to change all the bits. Faster video scrubbing (Fast FWD/RWD), meaning skipping ahead and rewinding will be quicker. More people can enjoy the server if the server doesn't have to work as hard and you get the highest quality picture you can. Hence this site was created to educate users on the optimal settings for Plex for the best experience.
While the below settings are being called "Optimal", it needs to be understood what "Optimal" means. These settings will help get every pixel from the server to you TV or screen that is meant to be seen. With that being said, if the server you are on or your own connection isn't substantial enough to receive all the digital bits you may encounter some buffering from time to time. In that case it's best to step your Video quality down to the next Quality profile down.
Mobile apps are treated differently, while up until now most of your apps you use with Plex have been free (Roku, FireTV, Android TV etc). Mobile apps are a one time $5 ACTIVATION fee that is paid directly to Plex from within the app. If you unlock it on an IOS device, then all IOS devices are now ACTIVATED for your account. If you ACTIVATE it while on an Android device, all Android devices will be unlocked for your account.