Here's a backup plan I developed after stupidly losing some data (fortunately, not too much) from a drive failure a few years ago:
1. Time Machine on a dedicated hard drive (6TB) in my old, but trusty, Mac Pro.
2. Backblaze. $55 a year (on the two year plan) for unlimited cloud storage seemed reasonable to me.
3. A bootable copy of my operating system SSD (with all applications, Lightroom catalog, backups, etc.) that I keep onsite.
4. A second bootable copy of my operating system SSD
and copies of all data drives that are kept in a safety deposit box. I try to update them monthly. Carbon Copy Cloner is used to copy my drives and it works great.
This plan might be overkill, but here's my thinking:
Time Machine is great, but useless if there's a fire, or my computer gets stolen. Ditto any onsite backups.
Cloud storage is great, but web recovery is slow. Backblaze's restore by mail option is nice (up to 8TB for $189 which is refunded if you return the drive within 30 days) but it still takes time. Also, as good as cloud storage is, you're relying on a third party to be around when you need them. Odds are they will be, but it's not 100%. Hence, the copies in a safety deposit box.
I'm probably still at risk for nuclear armageddon. I need to work on that.
Best,
Jeff