10 x 2.5 bay DELL R630, looking for best pool design for iscsi ESXi SSD storage

That would be my suggestion as well.

Well… the suggested layout remains multiple mirror VDEVs, or at the very least multiple VDEVs… you could experiment with 2x 4-wide RAIDZ1 VDEVs.

I suggest reading this and this.

Ultimately, it depends on your hardware and your use case: not all silicon is born equal.

You can also consider dedicating a single mirror VDEV to iSCSI and using the remaining 6 in RAIDZ1 (or 2) fo more traditional protocols.