This is the master reference thread for Lenovo Tiny https://forums.servethehome.com/index.php?threads/lenovo-thinkcentre-thinkstation-tiny-project-tinyminimicro-reference-thread.34925/
Patrick has alot of other writeups on the STH main site.
Personally my preference is Lenovo P330 or M720q:
- Supports x8 PCIe 3.0 low profile card or a 2.5" SATA drive
- 1xM.2 for M720q; 2x M.2 for P330
- 2 DDR4 SODIMM slots
- 2x 10G USB3.2 ports
- 1xM.2 B key supports non-wifi cards also (e.g. Zigbee/zwave)
- Heatsink technically supports up to 65w i9-9900 (though you leave alot of performance on the table for sustained workloads), but most come with an i5-8500T
There's also the HP T740 which also supports a PCIe card, but is a bit taller than 1U
The setup is fine since you're obviously trying to be budget conscience. I'd say cable management is really what you need more than anything else.
However, if you're handy with wood and a saw, or sheet metal and a brake (I assume you don't have a 3d printer):
Once you have all your NUCs in modular stacks, you can just run network cables and C13 power cords neatly along the front of the shelf, and have them input at the bottom of each stack. Then just tie your runs to each stack in a neat bundle and mount your switches to the underside of those shelves.
If you need to service a stack, you can just disconnect the stack in question at the termination points at the bottom of the stack and lift the whole assembly out, without having to play with wires. If you want to be extra fancy, you can even set up grooves or guides on the shelf to ensure the stacks are always placed in the correct position.