iCloud's optimize storage setting as well as image deletion.

I have recently turned on the "optimize iPhone storage" option since my device was running out of storage. I would like to know whether if recently shot images will now start losing its quality and whether if theses images if i now upload (to Instagram for example) will be in low resolution.

Also i would like to know if its possible to delete photos from my camera roll without it automatically deleting from my iCloud.

Thank You,

Kevin