setting up a pfSense router is cool.
you can use docker to run some local services and give them their own domain names with pfsense
if you want to progress further, you can use traefik to give docker/kubernetes services hostnames and get a cloudflare certificate to enable https on everything
NVMe drive to a SAS controller? Nope.
SAS drive to an NVME connector? That's probably doable, as NVMe is just PCIe, to which you could connect a SAS controller.
MiniSAS is just a plug that has four SAS connections running through it.
I'm running some gaming VMs on a Xeon E5-2699 v3. Good enough for older titles at 1080p, but the per-core performance isn't very competitive anymore.
Interesting, but mind you that some USB-C adapters may only be rated for 5V 3A or 12V 3A and will not be able to deliver the full rated 45/60/100W of power at lower voltages.
I tend to see 10G SFP+ modules for under $10, LCLC fibre cables are the same for ~10m lenghts and a NIC is, as you said, around $30. So fibre is cheap, but you can also occasionally find Aquantia-based 10GBASE-T (RJ-45) NICs which can do NBASE-T (2.5G and 5G) for $35, which is a good price, considering that these are generally more efficient than the older Intel chipsets and are just as fast.
That aside, your plan sounds good, I hope it'll work out well for you. USB3 adapters are also viable for 2.5G, so you can easily connect laptops and mini PCs that don't necessarily have extra thunderbolt or PCIe connectivity for a 10G NIC. What I suggest you avoid is the 5G USB3-based NICs, because in reality, they can only do around 3.5G and they also run much hotter and are significantly more expensive than the 2.5G variants.
Just wanted to say thank you for all. I'm set up with Logitech Media Server and couldn't be happier. The fact that it has a Truecharts app on TrueNAS Scale is just the icing on the cake.
If you allow some self-promotion:
http://robertzs.com/nvidia-vgpus-for-gaming/