There’s a features array near the end of the droplet object that you can check even before the first backup has been taken. If backups are enabled, it will be listed as an element in that array, the same as private_networking, ipv6, and virtio too (although Virtio is enabled by default for all new droplets, it was optional at one time). You can see a sample response body in the API call to retrieve a droplet by ID.