Love, Hate relationship with iCloud

iCloud Photos is not a backup, iCloud Photos is a syncing service. The purpose is to make your Photos Libraries on all synced devices identical. The central storage for iCloud Photos Library is iCloud. All devices upload and merge the photos into the iCloud Photo Library, and from iCloud Photo Library all changes sync to the devices and update the local library. Whatever you do with the photos on one of the synced devices, will automatically be updated on the other devices. All adjustments, all albums, all imports, and all deletions. More background information on iCloud is here: iCloud Deconstructed - Apple Community

iCloud Photos is syncing the photos, but it does not keep an archival backup. While working with iCloud, think of iCloud Photos as the primary working storage of your photos. Independent of how many devices you are syncing with iCloud and are mirroring the files in iCloud, the file in iCloud is the only copy. If you delete photo, it will be deleted from iCloud on all devices. To recover deleted images or videos you need a separate backup, preferably a local backup.

We cannot know, what you already tried with Apple Support to find your photos in iCloud. Just to be sure, you checked iCloud using the web interface at www.icloud.www.icloud.com and have you tried all your AppleIDs at this web page?

There are possible reasons, why you are only seeing a few photos there. Only one Photos Library can sync with with iCloud at a time. Photos may have switched to a different library, if the drive with the current Photos Library has become disconnected or unreadable. For example, Photos 4.0 on Mojave cannot use a Photos Library, that is on a Time machine drive.

Have you been using iPhoto or Aperture before 2017? In that case I would check your Time Machine backups for older iPhoto Libraries or Aperture Libraries, you could check the backups for the original iPhoto Libraries.

There is one additional complication with iCloud Photos. if you have had the "Optimize Mac Storage" option enabled to save storage on your Mac, the Time Machine backup or a clone of your Photos Library will only contain at the current local copies, older photos, that have not been used in a long time, will only be in iCloud. The Time Machine backup of an optimized library is usually incomplete. If your iCloud Library is optimize, you have to save the photos by exporting them. That will force a download from iCloud.

Apple Photos is a sync service. iCloud Backup handles your system.

It's important to note this difference when talking to support.

Restoring from iCloud won't restore your photos, you have to make sure you launch Photos and check that it is synchronizing your photos from Apple, you might need to leave your Mac on for a good while (3 days for me with 111 GB of photos), before all your photos will sync from Apple. This depends on your Internet transfer rates and a number of other arbitrary factors.

I hope this helps,

Kirk

I am paying for iCloud because of the syncing between my devices and because it is an offsite storage too.

• Off site storage: If my Mac is lost or stolen, or my house burns down, I can recover my photos from iCloud. The off-site storage is an added security, even if iCloud Photos does not offer a backup history. Because of the missing history iCloud is no protection from user errors, like accidentally deleting all photos and videos and does not qualify as a full backup.
• Syncing: I found iCloud Photos being the best way to transfer the photos from my iPhone and iPad, because it supports the new image formats HEIF, the Portrait Mode photos, the Live Photos. And all edits are transferred seamlessly, back and forth. There is no other way to transfer the edited versions and the originals paired as a photo, so the adjustments are reversible. This is especially useful when syncing the libraries between my Macs.

But if you do not need these advantages of iCloud, don't use it. Photos is working well without iCloud. if you do not need the syncing, the upload to iCloud will just be additional network traffic.