Yark will be able to do this in v1.3 releasing in ~1 month provided it has access to the playlists, I'm not sure how to do creds currently but I'll look into it.
For auth it seems the preferred way to login with Google is OAuth2, that's I believe what third-party apps use, e.g. Thunderbird uses it when setting up a new GMail account.
However, for apps that don't support OAuth2, there is also the possibility of using "App Passwords" [1], I've used one in the past and it worked well. (Update: I'm just reading it only works if 2FA is enabled, which I use)
> I'm not sure how to do creds currently but I'll look into it
Welcome to the nightmarish world of authentication to Google products, which all have 4 different versions of documentation and not a single one up to date.
Issue for downloading playlists: https://github.com/Owez/yark/issues/49