My only comment is that you aren't gaining anything by having your images on a SSD. I think you would be wiser to get a high-capacity spinning external hard drive to store all of your images, but keep your catalog on the SSD. You would experience absolutely no performance hit.
BACKBLAZE: I have been using Backblaze for just under three years. I would give it a 5-star rating; completely satisfied. Basically, you install it, tell it which drives not to backup, leave the computer on non-stop until all local files are transferred to the cloud, then forget about it. It runs in the background, checks regularly for new or updated files, and then copies them to the cloud. While I fortunately have never had a data disaster, I test Backblaze from time to time (per their suggestion) and pick a few files at random to restore. It has always worked perfectly.
One thing to note, Backblaze does not backup Lightroom preview files. The reason is that they take up a lot of space and LR can rebuild them easily. Backblaze has a whole list of file types it skips (like .exe files), but that list can be modified to your liking.
As for local backup, we all have our preferences. I personally keep two copies of all image files on internal disks (one SSD, one HD), and another copy on an external USB HD. That's in addition to Backblaze. Perhaps it's overkill, but I sleep well at night. I use the super-simple Windows app called SyncToy for the local backups, although I'm sure there are better, more powerful programs available.
John (no connection to Backblaze; just a happy customer)
I have same question as yuri. I need to replace my current external storage HDD to increase capacity to 12 or 16TB. Current library is 4TB of DNG files on an external USB3.0 drive (Seagate). LR catolog is on the C: drive which is a 1TB PCIe SSD. Will there be any difference in performance between a USB3.0, USB3.1/c and a Thunderbolt 3? I do quite a lot of panoramas and exposure bracketing which require merging functions in LR - I mention this because I'm assuming (rightly?) that LR accesses the DNG files from the external drive during those processes. Your input appreciated. Thx.