Apple Music + pluggable media library I'm newbie with iTunes/Apple Music doomsday machine, so probably my question is absolutely incorrect.

Is it possible to do following:


move Media Library to pluggable external drive
add songs to Media Library - it will sync songs to iCloud and make them available from any device using streaming
unplug external drive and listen music through streaming using same Mac
when plugging external drive again, listen or add music to Media Library on external drive


What I want to do is to have master copy of Media Library on external drive, while on the regular basis using streaming to listen music, to make Mac's disk empty enough.
You can do all of these five (five because your second question is actually two separate questions) by subscribing to either iTunes Match or Apple Music service. How you do exactly any of those five, however, depends a bit on which macOS version your Mac is running on.