I've been looking for this discussion so I could post a follow-up, but I couldn't remember where it was haha. Anyways, I found all of the memory files, and they are, in fact, saved separately from the screenshots. So, keep in mind that every time you "make a screenshot a memory," you are creating an additional file.
I want to delete them in hopes of improving game performance, but I'm a bit nervous to mess with those files.
Also, deleting memories in-game is buggy. It only actually deletes the first few that you try to delete.