Thunderbolt 3 docks usually bring their own USB host controller to the table. That host controller connects to the rest of your system over PCIe. So the dock ha

Thunderbolt 3 docks usually bring their own USB host controller to the table. That host controller connects to the rest of your system over PCIe. So the dock has its own private USB, so to speak. If you have a second Thunderbolt dock, you should be able to daisy-chain both docks, totally isolating your card from all your other USB devices while still maintaining that one-single-cable neatness.