it would help for the recommendation if we knew what version of the gen 8 you have as it will help with the recommendation, but in general with the limited needs you have currently and not needing to upgrade anytime soon, I would think the exact opposite, with ZFS being a memory hog, and if I remember right you need 2 of your 4 disks to mirror your zpool, although not sure on that one as it's been awhile since I played with ZFS. I do know some single core processors struggle with version 6 of Unraid, but you shouldn't have that problem. I would recommend looking through the forums as there are many with microservers using Unraid and that could help in your decision process.
~Burt