My organization system is similar to yours, except I have everything on a 2T external hard drive. I actually have one for my machine embroidery designs and one for quilting/ sewing/ crafts, etc. I only keep design files on my computer when I am working with them (creating design layouts, etc.) when I need to take the project to my machine, I transfer the information to USB drive. When I am finished with the project, or no longer in need of that particular design, I clear it from my computer and the USB drive. I have a complete copy of those external drives, which I store off site, in case of fire or flood.
With all my "stuff" on external hard drives, I am not as concerned if my computer decides to take a vacation on me (agh, Windows 10 decided to take over my computer. I had planned on the update, but not in the middle of a project.)
In conversation with my insurance company, she said my insurance would only cover $1,000. for "data" loss. WHAT??? I have many thousands of dollars in embroidery designs! We put a rider on our insurance for my software, computers, designs, machines (5), and working items such as stabilizers and thread.