I wanted to use a Dell Micro form factor computer as a host. To use this device, I needed to externally power the 10GB Mellanox card due to the built-in SATA on the mobo not delivering the full 12v needed to power the card. First, to connect the card I'll be using an adapter in the NVMe slot, NVMe to PCIe X4. As you can see, the specific MFF case I was using had a knockout that I was able to route the SATA adapter through. To route the PCIe cable through, I cut off a bit of the side latch and bent the cover a bit to give enough space to accommodate the cable. I did also have to use a SATA extension cable to be able to fit the SSD, since the adapter blocks the way. I could also have just bought a small M.2 NGFF SSD to install in the WiFi slot, but I was using what I already have on hand. This drive is to install Proxmox.
There are a few caveats as you can see. The largest issue I had to get around was that the micro pc just does not put out enough wattage to power the card. The only way I could power it is using an external source so I rigged up a power supply dedicated for the cards, although this does end up being a single point of failure unfortunately. The fan on top is simply powered via USB adapter.