All of the demos (and the walkthroughs) were performed with LEAP Motion. Using 5 controllers is great and playing with it just feels so natural to me. I love that thing to death.
The libraries are configured to play nicely on a standard MIDI keyboard first and foremost. Velocity determines the dynamics of the initial attack and CC1 determines the dynamics of the overall sustaining notes. You can use the interplay of two to achieve different sounding attacks as well.
There’s an Attack Range knob which determines the offset of dynamics that velocity can affect away from the main CC1 value, so if you were to set that to 0, your attacks would always start at your current CC1 value. I imagine that’s the default configuration you want to go with if you’re using a breath controller, although having velocity impact your attacks can add another layer of depth to your breath controller performance and I’ve heard of people liking it that way.
I’ve not tried it with a ROLI Seaboard. I imagine there would not be any problems since these instruments thrive with performance-oriented gear. The flutter, growl and vibrato controllers are all playable, and directly influence the sound.