How to delete photo doubles

What is on your iPhone is on iCloud.

If you had enabled iCloud Photos and then if you delete Photos and Videos from the iPhone then it is deleted from iCloud Photos too, and vice-versa. Also, it is deleted from all the devices that use the same Apple ID.

And if you happen to take a backup either over iTunes or iCloud after deleting Photos and Videos all the photos are deleted from the backup (iCloud/iTunes) too when you take the backup next time.

With my browser I can't see what phone you have but ios16 has a duplicates feature that comes up in the photos app.

It has also been announced fir the MacOS Ventura.

It may not list similar shots

It may not list duplicates that have been sync'd from a computer.

Find and delete duplicate photos and videos on iPhone - Apple Support (MN)

I have not had any issues, the only ones are on iphone 14 that we users could not beta test.