Does photo stream retain deleted iCloud photos? I would like to know as my iCloud storage is running out so I want to get rid of my old backup and make a new backup. I really want to keep all of my photos and memories on my phone.
On iOS, if I delete a backup will I still have all of my photos, even on my photo stream?
If you use Photo Stream as you mentioned your photos will be stored in iCloud separately and not in a backup, therefore it is safe to delete previous backups.

To further reduce backup size iPhone backup takes too much space