I agree with your reasoning, especially since external SSD have made it safer to carry physically as opposed to external HDD. But I mirror my internal NVMe SSD

I agree with your reasoning, especially since external SSD have made it safer to carry physically as opposed to external HDD. But I mirror my internal NVMe SSD to external SSD as the performance benefits of the former matters for me most of the time and when needed bootable external SSD is available at disposal. On macOS(not M1), Carbon Copy Cloner could create bootable clones of the disks. But I'm out of macOS for good as changes in Big Sur was too much for me, No offense to those who like it; but it seemed like a unicorn poop for me. Mojave was the last version which preserved the essence of macOS IMHO. Now I'm back to Linux, hopefully btrfs(snapshots) + Timeshift should recreate the same workflow.