- "RAID is not a backup" primarily because "you could rm -rf". ZFS snapshots cover that failure mode to the same extent that synchronization with offsite does, but cheaper. ZFS snapshots obviously don't cover other failure modes like natural disasters or a break in, so RAID is still not a backup.

- for ZIL to do its work properly, you need the disks not to lie when they claim that the data has been truly saved. This can be tricky to check, so perhaps think about a UPS

- if you have two M.2 slots you could use them to mirror two partitions from two different disks for your data pool's SLOG. The same could be done to form a new mirrored ZFS pool for the OS. In my case I even prefer the performance that a single-copy SLOG gives me at the risk of losing the most recent data before it's moved from the SLOG to the pool.