You do realize that the highest resolution iPhone camera takes 8 meg photos, right?
Which means that with the 16 megs threshold, you really don't have to worry about downscaling....
I am happy to see this service, although I've been using Dropbox for a while and it works well.
iCloud is so limited, including for stuff like data sharing, that it is practically useless and I cancelled my plan.
I just wish we can have Google Photos natively on Apple TV.
I just tested it and my original photo that was 2.3 MB has been downscaled to 1.2 MB. For me its not worth losing that much of the original using compression. Obviously none of my photos are more than 16 MP but it still compressed it a good bit. It is very misleading to say if its less than 16 MP, it won't be downsized. I probably will stick with iCloud/Photos.