GST is just Kubota for power shuttle, at least on their CUTs. Wet clutch with a hydraulically shifted transmission. There is usually a dry clutch in there too, not that you strictly need it.
Personally I never got the feel for the engagement timing in the couple hours I ran a L3?30 GST my brothers father-in-law has. I ended up using the clutch a fair bit. Probably would have gotten mostly onto the shuttle lever with a few more hours of seat time. Good transmissions, but still a bit more of a learning curve than HST, especially for precision work.