For something that uses this approach (metadata from spotify, music from yt) but with downloads, take a look at spotdl[1]. Very useful for mpd. Disclaimer: not my project, but I've had some success with it.
It will download any Spotify playlist or YouTube playlist as a bunch of individual MP3s, and do it fast. You can also paste individual song links to download them. Great quality and UI.
1. https://github.com/spotDL/spotify-downloader