As far as pricing goes, $5 per month for 100GB seems steep. SpiderOak offers 400GB for less than that and so does Nordlocker (though Nord has its own problems). On the other hand, iDrive has been offering a whopping 5 terabytes for a whole year for just $3.98 in a deal I saw just a few days ago.
Overall, zero knowledge backup is the best route, Backblaze plays at that, on the other hand I wouldn't touch any backup offering by Google with a 10 meter cattle prod. Grotesque that they reserve the right to snoop right through your files unless you first encrypt them externally via third party apps.