If I delete photos off my device,does it al

If you use the service iCloud Photo Library, deleting a photo from one device WILL delete it from all corresponding devices that are signed into your Apple ID. iCloud Photo Library is a syncing service and not a backup. If your content is in iCloud Photo Library, there should be NO REASON to delete them from your device unless you dont want someone to view that image.

And say I did NOT want someone to view that photo due to iCloud photos being shared on a company device, linked with my Apple ID. How would I be able to delete specific photos off an iPad, however keep them on my iPhone?