I suspect I already know the answer to this, but rather safe than sorry!
My Mac Mini at home serves as the final repository of our photos. Backblaze and TM backups take care of it.
Photos taken on the 8+ are uploaded to the 2tb iCloud storage, and synced over to my iPP, with the Mac Mini pulling down the original resolutions (or whatever that setting is called).
iCloud Photos is therefore switched on across my iOS devices, and the Mini, with the latter serving as the ‘system library’.
Over on my MBP, I have long since stopped using Photos - having mentally accepted that any photo-work gets done on the Mini. I actually forgot I still had a Photos library on my MBP. It hasn’t synced since July 2018, and iCloud Photos is NOT active on it. Still, it’s size is some 220-odd GB’s - which will be useful to jettison off the MBP…
I’m correct - given the above - that this can simply be trashed? As far as my setup goes, it’s outside the loop, so to speak? Anything I might be missing?