> That's because my worry is corruption of the entire Library, which Photos stores as one gigantic opaque file/directory abomination. My .photoslibrary file is currently 70gb in size, and I'm terrified of what would happen if it becomes corrupted.
It's a folder that acts like a file.
Right click > Show Package Contents works, and there's an "originals" folder that should have all your photos in normal everyday files.
Instead of being organized by album, they're all thrown together with the filenames as UUIDs instead of the original name, or any useful name whatsoever. The editing steps I've applied to the raw files are, of course, not present. The important parts are all stuffed into a single giant .sqlite file, it looks like there may be other shared resources as well.
The point is that - from a data safety standpoint - it would be better if all of the internal metadata were persisted per album, if not per photo. That way one corrupted file would only affect a small subset, rather than causing me to lose the whole library.