What are my secondary backup options?
More than a 'cloud drive' solution, you should be looking for a 'cloud backup' solution. Backblaze and Crashplan are popular options, but there are a variety of possibilities with different features , such as Arq or Tarsnap.

A bootable copy of your main drives would be an additional insurance against disaster; you can use a software like SuperDuper! or Carbon Copy Cloner.