Poor picture quality when watching remotely using smart tv or ipad

What are you seeing on the server dashboard while streaming a video remotely?
Does it show as remote or indirect?

Exemplary screenshot from the "now playing" section
https://support.plex.tv/articles/200871837-status-and-dashboard/

If you’re only getting an indirect connection, you might need to troubleshoot your remote access configuration.

https://support.plex.tv/articles/200931138-troubleshooting-remote-access/

If that’s not it… try disabling automatic quality.
Is your server powerful enough to transcode those files (if needed)?