Test it. Download a small batch of full resolution photos from iCloud that are optimized on your iMac and see how it turns out.
Thanks Ira, but any testing on Photos will have to wait, because things keep changing. For example, all the photos are now on my iPhone (which I've never had before) and these photos include a bunch that I removed. The photos on iCloud can be the last thing dealt with, so perhaps I was wrong to identify the issue. My priority is to get my iCloud mess sorted out before commissioning new iPads.
Over time my iCloud interface has become something of a jumble and I’d like to get it sorted out. What I want is to use iCloud only to have synchronization between iMac, iPhone and iPad for such things as Mail, Message, Contacts, et cetera.
We have two new iPads, still in the boxes, because I don’t want them to start life with a bunch of unnecessary stuff that needs to be cleaned up. I’d rather do the cleanup first.
How do I undo what’s been done and start from scratch?
