The kmix was a little confusing for about a week, just because it has so many options built in. as a basic mixer, I find it very direct and flexible. If I want to sample anyrhing going into the kmix I can, and I can separate it from the rest too.
I haven't experimented too much with midi control of the digitakt via kmix. I tried controlling the mixing screen of the digitakt with the kmix faders, but each kmix midi map (you get 3) is transmitted over a unique midi channel. If I wanted it to work there would need to be a unique cc message for each volume control on the digitakt, but there isn't. They are all 95 I think