ZFS RAIDZ is not a performance-oriented configuration, all ZFS documentation I have read so far indicates that the average read/write/throughput of RAIDZ array is supposed to vary from "very close to ...

The pool is not the raid. Now you're just not making any sense - the pool is the equivalent to the volume group in lvm. This is a common misconception. You have a bunch of disks. You say I want a pool ...