iCloud Photos

Good afternoon alfie9000,

Welcome to the Apple Support Communities!

I understand you have increased the amount of iCloud storage that you have to accommodate all of the photos on your iPhone and on your MacBook Air. If you enable iCloud Photos on your Mac, any photos or videos that are on your Mac that are not already in iCloud will be uploaded so that the photo library will be identical on both devices. No photos will be erased from your iPhone, and no duplicates should upload.

The resource below explains how iCloud Photos works to sync all of your devices. Please read it carefully so that you have a good understanding of how additions, deletions, and edits will affect your photos on all of your devices. Remember that you can choose the Optimize option on your iPhone or Mac to free up space on the device by keeping the high resolution versions in iCloud.

iCloud is a syncing service, not a photo archive system. Make sure you back up your MacBook Air regularly with Time Machine. You can also export albums and other media to an external drive to have another copy of them.

Set up and use iCloud Photos

Export photos, videos, and slideshows from Photos on Mac

Happy New Year!

I have a similar problem with multiple libraries and iCloud photo storage... I wonder what the efficient answer is and what the answer to your questions are.

In the meantime. I have installed on my mac air (mojave) a program called "Duplicate file finder".

So far I have found it to be very useful. With it I have been able to delete a lot of duplicate files. With photos it has a nice added feature that compares similar photos so that you can choose between a blurry version and one that isn't and other similarities.