Help with PC build/ 10 bit monitoring.

So I want to build a mini-ITX PC but also be able to output to a 10bit reference monitor in resolve. Problem is that the board only comes with a single PCI-E slot for the GPU and no thunderbolt port so the mini monitor is also out of the question.

Is the https://www.blackmagicdesign.com/au/products/intensity via USB 3.0 a viable option for colour correct reference monitoring?

Yes, but USB3 support is problematic. It may work fine or not at all. Depending on the motherboard USB chip. You would need to test it.
You should be also able to find mini-pc with good gaming card and Thunderbolt 2 or 3, no? ZOTAC?
Or things like this: https://www.msi.com/Backpack/VR-One-7RE

thanks for the info. Looks like I'll be restricted to a motherboard with thunderbolt.

Here's one that I've found https://www.asrock.com/mb/Intel/Fatal1t ... ing-ITXac/

Looks quite good.

Yes, looks decent.