I want my music player widget to only display the covers from the songs i listen to on soundcloud and spotify, but when i play a youtube video it also displays its cover. Is they a way to stop that from happening?

General
1

I have the same problem with my wallpaper.

2

No, you can force it to use one player but not two, to force a single player select it from the app settings

3

You can try this in the visibility formula:

$if(mi(package)!=com.spotify.music,NEVER,ALWAYS)$

5

I know you can limit the preferred players now and SoundCloud and Spotify are on that list.
In the app menu, Settings > General Settings > Preferred music player