If you really want to remove everything from your mac simply drag the Photos library to the trash and empty the trash - there is no undo for this -- and if 27 BG is a problem you need a better solution as you are very short on space even after recovering that
And note that you do not have a backup since you deleted the photos from your Mac - a backup requires two or more copies of the same data on different drives - putting a copy on a different drive and deleting the original is not a backup and with no backup you are 100% guaranteed to lose your photos sooner or later
LN