One other problem that I thought of, storage device write cache. ZFS was originally written when HDDs had write caches that could re-order writes, (aka elevator seek). On power loss, (or OS crash), that could cause data loss.
At one point, (around 2010), Sun Microsystems recommended disabling HDD write caches when using ZFS because of this problem.
Eventually this problem was overcome by implementing and using write barriers. This meant that all the preliminary writes for a ZFS transaction, (aka data write), could be known to be flushed to media, (HDD sectors, SSD / NVMe flash memory), before the final write that activated the prior writes. This meant that ZFS was still always consistent on stable media and would not lose data on power loss or OS crash.
However, USB controllers, (with or without hardware RAID controller), could still implement elevator seeking with their write cache. And it is possible that low end flash storage devices, (whether that’s USB, SATA or NVMe), may not implement write cache correctly. Expecting low cost / low end storage devices to be perfect would be asking too much.
So, caveat emptor, (buyer beware).