Is there a way to see what's there?
I think the only way to see what's in an iCloud backup is to restore from it.
Also, what advantage is there doing it via from device?
I don't recall if a computer running iTunes ever gives you the option to restore from iCloud. I do know it would give you the option to restore from any local backup you had made.
When setting up from the device after performing a reset, I know it will prompt you to restore from your iCloud backup or "set up as new iPhone."
If you have iCloud Photo Library enabled and your entire camera roll has been synchronized with iCloud, you shouldn't have anything to worry about when it comes to wiping and restoring your phone.
When you restore from iCloud after resetting and doing the on-device setup, it even lets you start using it before it's fully restored. For example, iCloud Photo Library downloads thumbnail images for all your pictures and videos, then starts downloading the most recent ones and the others are downloaded on-demand as you try to access them.
I choose the "optimize iPhone storage" option for iCloud Photo Library because I know the full uncompressed picture or video is in my iCloud account.