Jamiesipad wrote:
If I delete the music library from my MacBook, will the music on my iPhone and iPad remain on those devices, or will all of my music be deleted on all of my devices via iTunes Match?
When you delete music from one library or device and iCloud Music Library (AKA Sync Library) is active, then the content is deleted everywhere. Rather than deleting content you should use the right-click > remove download option, which frees up local storage but keeps the item in the cloud allowing it to be streamed or redownloaded at a later date.
Ideally you would make a complete backup of the current state of your library on an external drive before removing downloads, just in case it turns out you have an mismatches, failed uploads, or you mistakenly remove something from the cloud in error.
Note that you don't need both iTunes Match and Apple Music at the same time. Apple Music includes all of the features of iTunes Match.
tt2