Hi @timmyx, great guide, managed to configure my own setup following it.
That's because unraid will create pre-configured container with a docker create command and you will need to start it with a docker start command to apply settings.
That way the run script basically boils down to docker start -a youtube-dl and you can edit everything else with unraid GUI.
You can read about those docker commands here:
https://docs.docker.com/engine/reference/commandline/create/
https://docs.docker.com/engine/reference/commandline/start/
I also had to modify the container and add aria2 downloader because youtube roughly throttles my downloading speed after ~10 videos. Example settings for this are:
--external-downloader 'aria2c'
--external-downloader-args '--console-log-level=warn -c -x 16 -s 16 -k 1M'
It's not great either, but at least I can get 1MiB/s (without aria it's only about 50KiB/s).