The information on this Wiki page https://openzfsonosx.org/wiki/Performance may need to improve. I have installed the 2.0 on MacOS 11.4. But seems the /etc/zfs/zsysctl.conf is not an OOB configuration file. It is missing after the installation. I tried to follow this wiki page to reduce the memory consumption but failed. I wonder what the correct kstat parameters for the 2.0 release.
You can see the memory usage is now about 5G. I guess for a PC level ZFS 1G memory for ARC and cache is more reasonable.
And you can see from the screen shot there is something wrong of the arc_stat tool OOB.