It supports Spotify, Google Play Music (Client) and the "NowPlaying"- plugin
To switch between these "player types", right click the skin, open "Variants" and click on the player you want to use.
To change the size, colors and the player for the "NormalPlayer", right click the skin and click on "Open Variables".
To switch between songs, you just have to scoll up and down on the "blur" area of the skin. Click on blur area to "slide" the album cover in or out.
Edit: i figured it out. nm