I have only one iPhone 6 plus a the moment. I had to return an iPad mini 3 because no one could help with the photos at either Verizon or Apple. In settings I do have the photo library turned on and photo stream turned off. I have the full size versions of photos on the iPhone..or so I believed until a tech call today. I have the optimize iPhone option turned off so that full size versions would be available locally for my own WiFi or Windows cable import. I don't see any way at iCloud.com to download or import more than one photo at a time from iCloud to my computer. After talking to an Apple tech this afternoon, I am under the vague impression that photos are first stored on iCloud and then downloaded to the iPhone in full resolution. This makes no sense but it was after I stated I thought I had full resolution photos on my iPhone that I was told this. If true, it makes backing up and restoring photos all the more difficult because I can't be sure what is a full res file and what is not on my iPhone. The way I have optimize turned off, I don't now what reason there would be for any optimized photos to be created. I have over 200 GB of iCloud storage so there is no need for optimized copies there.
I believe these settings worked well for quite a while and I am not honestly certain when the photo upload stopped. It can't be too long as the numbers waiting to upload have increased from over 2,000 to over 4,000 in under 2 weeks. Of 21,000 photos on my iPhone, about 17,000 are supposedly on iCloud. I see no difference at all in the number of photos actually listed as on iCloud. Therein lies another problem. I can see the first window of photos which says at the bottom there are 17,000 photos there. But I am unable to scroll down from the opening window of photos to see any except those that first appear. The tech and I have been thinking that's due to the large number of photos but at the moment I am doubting even this. I have boards on Pinterest with about 10,000 pictures and no problems at all trying to view them or scroll down the screen and all show immediately. So I don't think its just a matter of too many files to display on my computer or with Internet Explorer 11. What might be one solution would be to install iCloud for Windows on my computer. I will not so this again after doing it several years ago and finding files deleted and files sent to iPhone, etc., all at the rules of icloud or whatever iOS at the time. There is no written statements that iCloud for Windows should be installed to use photo library. Throwing in one more tech opinion, the senior tech support at Comcast, while checking and reviewing the WiFi connection I am using, discussed her own PC setup and wat options she has on iCloud.com and it's different than what I have. We decdied it had to be because she has iCloud for Windows installed on her PC.
Thanks for your interest. I'll be waiting to see what you think.