YouTube and YouTube Music are sharing same user collection if you are using 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, followed channels become favorites artists and liked videos, favorite tracks.
Even if there's no YouTube Music official API provided by Google, we have separated YouTube and YouTube Music.
That means if you are using YouTube on Soundiiz as destination service we will match with the most popular video, often the official music video.
If you are selecting YouTube Music as destination, we are matching with audio only tracks available.
Unfortunately we are not able to manage Albums, as it's a kind of saved playlist to YouTube and we have no access to this kind of data with the YouTube API.