They limit the bitrate to 4mbps through their relay servers though, which prevents HD streaming.

The relays only come into effect if the client isn't able to form a direct connection to the server. However most are able to do this without issue and its automatically for the most part.

Good to know, thanks. I used Plex as an example since more people know what it is, but in practice I would use Jellyfin for media streaming, since it's open source and doesn't use dark patterns. But you also need to manage tunneling yourself...