I’ve got ZFS on my older NAS which is a FreeNAS box I build myself a while back (an old HP N40L), the Synology one is using BTRFS (only because it doesn’t support ZFS). That being said, I’m well aware of bitrot, the RAID is to protect against a drive dying, and the vast majority of stuff on the NAS is stuff where a flipped bit isn’t going to be the end of the world even if the file system doesn’t catch it. For stuff that’s more important I keep multiple copies of it or and/or have a backup in the cloud.
I can’t speak to the netboot part personally but I’ve had Docker data folders mounted via an NFS share for a while now, and while it worked fine, I’ve just in the last week or so swapped them all back to local storage for performance reasons (typically anything involving a SQLite database), so depending on what services you’re running via Docker, check that your network speeds aren’t going to be a bottleneck for it. (My home network is only 1G for reference so might not be a problem for you).