1. Open Plex app on your apple tv & sign into your account if it's not already

2. On the main screen on the left side scroll all the way down to settings.

3. Under video quailty set these settings (see photo for example)

Auto Adjust Qauity - OFF

Home Streaming - Maximum

Internet Streaming - Maximum

Play Smaller Videos at Orignal Quality - ON

4. Under advanced set these settings (see photo for example)

Allow Direct Play - ON

Use Old Video Player - OFF (May be missing or unchangeable)