[lanterk]

For 9, I would just go with youtube-dl -f 140 (or 141 in some cases). No reason for lossy->lossy conversion.

[Houshalter]

Hmm I don't see any documentation for that format code.

I chose mp3 because it's the only format my ipod accepts. The formats it downloads by default won't play, even if they might be higher quality.

[rg3]

youtube-dl -F VIDEO_URL will give you a list of formats in YouTube, that you can choose using the -f option. DASH streams contain only video or only audio normally.