Is it ok to delete all iPhone old backups and keep only the most recent?

Yes it is absolutely OK to do that. Keep the backup(s) that you think is the most relevant to restore from if you need to. Delete the rest.

Axel F.

Well, not just you. iCloud is unusual in the way it works. Most times if you sync photos, to say, Google Photos, they stay in Google Photos even if you delete them from your device. Partly because of Google photos and a dozen other archiving services Apple designed iCloud to have a different function, rather than just duplicate services already available. Here’s a more detailed explanation→iCloud Deconstructed - Apple Community

Ok a few years back I backed up everything onto iCloud , I was paying for extra storage, and the iPhone 8+ still wasn’t optimizing so it was running out of memory , I have an iPad Air also , so I also put it into the storage on that , and turned it off ,then I deleted the things off of the phone that were already put into iCloud , when I turned around , it was almost spooky , it went on a search and destroy mission and completely wiped out almost 2,000 family pics and videos from all of the iCloud and anywhere it could find , then as soon as I powered up the iPad , it marched right in and wiped it out also , Apple support tracked all of it , unfortunately had no explanation , after 10 hrs + on the phone .

iCloud is not an archiving service, it is a syncing service. So anything you add, delete, or modify on iCloud or any device connected to iCloud will be mirrored on all of the devices sharing an iCloud account. Thus, deleting photos from iCloud will also delete them from your phone, iPad or computer using that same iCloud account.

iCloud Backups are completely independent of data synced to iCloud. There is no overlap.

I appreciate that information, first time I’ve heard anything that makes any sense

I must have goofed up somewhere , as I really was careful not to mess with anything in the cloud , that’s where I figured it would be safe , the people in service could see my , “trail “ and didn’t understand it either , nor could they understand why the phone wasn’t optimizing itself after backing up , I seem to be pretty good at finding a way to mess things up , usually by accident .

You are welcome.

Axel F.

Go to Preferences / Devices to see the backups present. Right-click on each for options.