I am the least knowledgeable on this, but as it's Google's cloud service, anything you choose to back up, and to sync in the Google account settings, goes via Drive.
Which brings us back to other threads where some have found turning off Google + (Plus) and / or many sync options in their Google account improves battery life.
There are pros and cons of disabling Google +, and un-syncing photos etc.
I use Kies, Samsung and Dropbox for the little back - ups I need. I just directly copy my photos, ripped music files and docs to my pc, but I am old school.
I do use Google for syncing apps, contacts and sometimes Calendar, call logs and sms. I can do these without Google + being enabled. I cannot now leave Play Store reviews without activating Google +, grrr!
(For 'Disabled' read 'Turned Off' on many models.)
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