The default configuration includes everything except for system files to be backed up. That also includes external USB drives. This will work for most people. It can, of course, be customized to each person's liking.
Backblaze creates a zip file of all your files for you to download, thus decreasing the amount of data you need to download and increasing the speed of the download since it's one connection instead of multiple that need to be opened and closed for a list of files.
Once set up on your computer, Google Drive will create a folder that will sync with the cloud storage. Only files and folders within that folder will be backed up to the cloud and there's no way to change that.
When it comes to ease of use most cloud backup service are pretty easy as it is just one signup, with Arc you need to download install and activate it to then register for an Amazon account, this extra step may be troublesome to some people or just annoying.
Both for free and paid accounts, there are monthly transfer limits. That is, the user can only upload/download a certain amount in one month. For instance, it is 10 GB/month for free users. The transfer limits, maximum and current can be viewed in the user's account page.
Encryption allows the use to access their files with only their own keys and the deduplication saves on costs of storage as any duplicate file will be removed automatically. So not only is the platform safety minded but cost is taken into account for the user as well.
I don't use their consumer service, but rather their B2 cloud storage buckets to store the backups I make myself. I can't think of a single negative aspect of it... The price is staggeringly low, they offer more bandwidth than I can get from Comcast, and the API is really easy to just dive right in a...