I have a KICKR SHIFT.
Right now, there is no gear display in Zwift. You can pair a Wahoo head unit (ELEMNT, BOLT, ROAM) and it will show gear information. There is also a thread here about using an ESP32 display to get gear information, and even a mod to have a window you an overlay on Zwift to show gears.
Zwift can add it with an update, I’m sure.
I don’t think the 10Hz (race mode) is on the SHIFT.