Hello Tom,
One that supports the highest possible data transfer rate (40000 Mbit/s).
I personally use this one: i-tec Thunderbolt - Thunderbolt 3 (1.50 m, Thunderbolt)
This allows me to use 2560x1440 at 144hz or 4k@60hz, which is sufficient for my purposes. I don't know to what extent 4k@120Hz would be possible with the right combination of cable and Surface.
Hope this helps!