Trying to Understand iCloud Photo Storage

[rich in distress]

graylocks wrote:
… what I see on my phone are reduced versions? I would have thought it would have a little cloud icon on it if that's the case. does 'upon request' mean that when i want to post a photo to Facebook or Instagram it's not pulling it from the reduced rez version on my phone but the full rez version in iCloud?

The little cloud icon happens on files.app or with offloaded applications. Syncing photos resembles using the address book.
I don’t know what size is used for social media. Maybe reimport one of your photos and get info to check.
Worth mentioning:
Settings/AppleID/iCloud/Manage Storage will let you see how much space your Photo Library uses in the cloud.
Settings/General/iPhone Storage will show the size of your Photo Library in the phone.