1. When you use Messages in iCloud or turn on iCloud Photos, your content is automatically stored in iCloud. That means they're not included in your iCloud Backup.
Ok meaning, as long as I don’t’ turn on the iCloud Photo, and I checked all the rest of the apps at the iCloud Backup Tab, the phone will backup all files (including Photos) to the iCloud whenever I put the phone to charge in a connected wireless environment.
In the event when I need to restore my iphone, I choose the “Restore from iCloud Backup” option.
Am I right?
Yes.
I'm not sure how the backup size is calculated though.
You should consider leaving iCloud Photo Library turned on.
Nice! Which phone are you using? Still have applecare? Free replacement is good.
Anyway, I always leave iCloud photos on devices I wanted to upload to iCloud automatically. 5gb is a bit too less, 50gb for 1 dollar plus a month it’s worth it to me.
Hope that helps cheers