My wife and I each have an iPhone 6, and we have an iMac. All 3 share an Apple ID. I have iCloud photos turned on for the iMac (keep originals) and my iPhone (optimize storage). Can I also turn on iCloud photos on my wife's iPhone? I assume that this would also use optimize storage, and this would allow all of our photos from each phone to be centralized in one iCloud photos database? Any risk here? I don't want to mess up our iCloud photos - we have about 50,000 pictures on iCloud.