New ESXi/Proxmox/FreeNAS server build advice

[Choppatron]

I am looking for some advice on components for my home server build. The purpose of the server is to provide NAS storage (probably FreeNAS?), VMs and various Docker containers such as PiHole and Plex etc for my home, as well as a playground for testing and learning other tech like Kubernetes and Rancher
The base OS/hypervisor will be either ESXi or Proxmox VE.

So far I am looking at the following...

Case
2U short depth (400mm) with 4x hot-swap 3.5" drive bays.
https://www.inter-tech.de/en/products/ipc/storage-cases/2u-2404s

Motherboard
SuperMicro X11SCM-F micro-ATX LGA1151
https://www.supermicro.com/products/motherboard/X11/X11SCM-F.cfm

CPU
Intel Xeon 2146G 6-core, 12 threads, 80W TDP.
https://www.servethehome.com/intel-xeon-e-2146g-benchmarks-and-review/3/

Boot/OS Drive
250GB Samsung 970 EVO Plus M.2 SSD.

Storage Drives
4x 2TB (recycled from my to-be-retired QNAP).

I have some questions about some remaining components...

1. CPU cooler, I'd like this to be as quiet as possible. I am thinking of either the Noctua NH-L9i (probably to high TDP) or the NH-L9-x65 (maybe too tall). Any other coolers I should consider?
   
2. RAM, the motherboard supports DDR4-2666MHz, is it worth going for the faster DIMMs or would 2133MHz be adequate (and considerably cheaper).
   
3. ZFS ZIL SLOG, there is a spare M.2 slot and thought about adding a 32Gb Intel Optane drive for this. Again, is it worth it or perhaps something else?