I have an 2 iMacs (2017 and 2013), one running Mojave (2013) and the other Catalina (2017), any changes with my photos work flawlessly with Mojave and are updated on my iOS devices. Photo's do update on Catalina however my folder structure is a complete mess.
I have my albums organised by year and event (not using any sub folders). I've checked photos via the browser on iCloud and again the structure looks fine, the issue is obviously with Catalina. I'll disable iCloud on the Catalina Mac and manage my photos from Mojave until Apple comes up with a fix.
Tempted to run a repair on Catalina Photos, however I've seen a few posts where this has not worked. Manually reorganising by photos would be an option if I didn't have so many (150k photos)
Hoping this will be fixed in 15.1.
Just to add further to the mess, when clicking on a photo within Catalina to add to an existing album, or create a new one, the list of albums is in a completely different order to the list of albums on the left hand side... very strange! If you are contemplating Catalina and value your photo collection my advice is to wait until Apple sort it out.