Sycraft
Sadly Focusrite seem to employ the slowest driver writers in the known world so they'll get around to writing thunderbolt windows drivers in about 2040.
FWIW, We don't have "PCIe via Thunderbolt" drivers available for Thunderbolt 2 under Windows.
Any Thunderbolt 2 audio interface connected to a PC is currently running "Firewire over Thunderbolt".
We do have official "PCIe via Thunderbolt" drivers available for Thunderbolt 3 under Win10.
You have to be running one of the latest Z170x motherboards (Skylake) that supports Thunderbolt 3 via USB-C connection.
Microsoft claims TB3 support should be backward compatible with TB2 and TB1... but they don't guarantee it.