If you delete photos in the OneDrive app on the phone, they're deleted online.
The OD folder in the Photo isn't the issue.
Those are 'online', the OD App in Storage Sense jumped from about 1.62 GB to almost 8.42 GB over night (1.62GB originally plus 6.8GB = 8.42 GB) and that GB is now in the phones storage. I haven't done anything different as in I only upload photos to OneDrive online as needed "maybe" every 3 days otherwise it's OFF and only 8-9 photos at a time. I have only have 114 MB of photos on my SD card and 208 bytes in the phones storage. In Storage sense the Phone's system almost doubled to close to 10.5GB -in a 12 hr. period. "Moved" meaning mysteriously, I did not download them or open the OD Folder in Photos and saved almost 7GB of photos to my phone. ALL the photos in my online OD account (which are still there) copies of those photos arecon my OD app on my phone (not the folder in Photos) and that is stored on my phones storage...thus the almost 7GB jump in the phones storage in a 12 hr period. I did nothing different, MS Windows Phone Support /MS OneDrive Support, Nokia Support all say that should not happen, and are baffled.
***I switched numbers accidently in my original post..OD app on my phone jumped from about 1.62GB to 8.4GB not the other way around and that is stored on my phone.
And where do I find this "And do you have "camera roll backup" enabled in the Onedrive settings" there are no settings on the OD App on the phone, 0 settings. Menu: 'create a folder. refresh, sort by, recycle bin, send feed back,