there is even a special adaption for the APC 40 for Kyma from Delora! It should give you all the features of the Motormix within a bit more modern package then the orginal Motormix.
Douglas support is great and his software works perfectly with Kyma!
Anyway i personaly decided to go for a used Motormix with Kyma because it has those nice flying motorfaders!
Which mean instant recall and hands on even with roll the dice.
But for using Kyma Live i would strongly recommend the APC 40 over the Motormix.
The Motormix is heavy...i mean really heavy. In the studio this is a nice thing.. on the road.. hmm.
I used the APC 40 for some time with my own OSC bridge build with Osculator before i found a JL-Cooper CS 32 MIDI.. which is very very rare but for me still today the best portable controller for Kyma. It is tiny and simple but with Kyma and Osculator it is very very powerful.
Anyway the APC 40 should work smooth with the vKA from Delora and is a fast to setup and a dynamic solution which works with any VCS out of the box..
I hope that helps a bit.