jms54 wrote: …I did not select any of the three options and the "PHOTOS LIBRARY" down loaded completely all 518 +GB's.
That's quite weird!
And that's a big Library. It might be worthwhile to divide it up. I have a Favorites Library, a Wife's Family Library, My Family Library, Work Library, and so on. Favorites has the best of them. I have a lot of pictures that I don't need to see or share with my phone.
I think the downside of a large library is mostly time. Photos spends a good bit of time scanning the entire Library to record details that will make searches quicker. So searches work fine, but when something changes there can be delays and slowdowns as it re-scans. Photos checks new imports for duplicates, and that can become cumbersome. Also, I spend some time adding keywords and captions and titles, but I really only do that for my Favorites, since doing it for the whole pile of pictures would wear me out. Just thinking…