How long does it take to restore from an iCloud backup?
There's really no definitive answer to this as a lot comes down to network speeds, bandwidth, what else you're currently doing with the device, and so on.

That is why you're finding that "Googling online it says it can take 1-4 hours per gb to restore from an iCloud backup" - because there's just too many variables involved. In fact, there are places in the world where 1Gb of data would take even longer than 4hrs to download.

As for your thinking that maybe it would be "faster to restore from iTunes", then it certainly would be if you're talking about a local iTunes backup that contains all of the photos and videos in question. Keep in mind though, a full "restore" means you're restoring your entire iPhone with what's in that backup, meaning that your phone ends up losing any data it currently has since that backup was made.

However, if you have all of the photos and videos also stored on your computer (e.g. in the Photos app on a Mac, etc) then you could use iTunes to sync across the photos/videos you want from that source rather than restoring your divide from a backup.