Same problem:- upgraded to 12.7.4, ios 11.3.1 on an iphone X bought last week. Apart from the fact that it was screwed, straight out of the box screen going haywire - "A lemon" - Apple renewed it with no audible apology or concern for the 2 weeks I had wasted trying to "fix" it and waiting for the first available appointment at the Genius Bar - must be very busy). Phew!
here is what I did:-
1) Set my 7 Apple devices to ignore syncing photos
2) Deleted all photos from the 7 devices - they are all backed up in 2 places in amongst 26tb of storage
3) Did NOT downgrade to iTunes Virusware 12.7.3
4) Did delete the absolutely Rubbish Google photos app - where's the sorting by name order for the people who actually organise stuff in "Photo Folders" ? Nowhere? It's for little girls and boys who like to see last week's pix
5) Did copy and paste to my 1tb of Google Drive storage all the vids and photos I will ever want and DO use Google Drive
6) And said bibi to Apple's time wasting rubbish and photo syncing - i will be deleting their music sync too soon when they mess that up
Come back Jobs all is forgiven
Cook you're a disgrace
End of story
Life's too short