The main difference from their previous versions (CK3 and CK4 from 2016) is the bigger display (LCD 1.8", 160x128) with menu and my own firwmare code.
On display I got a menu and drawn keyboard layout with cursor and can edit key mapping on layers, sequences/macros and everything else I needed including demos and a game .
More info about them and the firmware on my website and topic here.
Apart from that, they also have heavily reduced (cut off) rubber domes, making them much softer and nicer to press. CK6 has about 23 gram force, travel distance is probably 1-2 mm. This is a process I started already in 2005 (and CK7’s keys work fine already 12 years so).
My lightest such mod resulted in 9-18 gf (varied by keys, depends on foil thickness), described there.