I would advise using ZFS on Linux over ZFS on FreeBSD. You may find this somewhat surprising if you know my post history being a major FreeBSD advocate, but I

I would advise using ZFS on Linux over ZFS on FreeBSD. You may find this somewhat surprising if you know my post history being a major FreeBSD advocate, but I have run into a somewhat surprising and persistent (and known, but not to me when I started building) issue with FreeBSD's USB Mass Storage support. This issue does not happen on Linux. This is among several issues I noted which affected my ability to make a budget-friendly homelab NAS. Since you are using an M.2 drive rather than a USB drive for your boot drive, you are not affected by the issue that affected me. But I've reached a point where I would not trust FreeBSD to not have weird and esoteric hardware issues that could affect performance or reliability for storage. I'd recommend using ZFS on Linux (Note, I still use FreeBSD as my primary OS for my personal laptop).