YouTube and YouTube Music share the same user collection if you are using the same Google account for both services.
For example, if you are converting a playlist to YouTube, you will also see this playlist some times later in your YouTube Music interface.
Also, following channels becomes favorite artists and liked videos, favorite tracks.
Even if Google provides no YouTube Music official API, we have separated YouTube and YouTube Music.
That means if you are using YouTube on Soundiiz as a destination service, we will match with the most popular video, often the official music video.
If you are selecting YouTube Music as a destination, we are matching with audio-only tracks available.