Yamaha DTXpress/DTXplorer/DTXtreme

I don't use Cakewalk but I think that a GM kit is selected because there is
a midi program change which is sent by Cakewalk. In order to prevent this
change, the most easy way is to put the mute fonction, therefore all
information which are coming through the channel 10 will be ignored. The
other way is to change the program change settings of the DTXpress, but it
is maybe more complicated.
For mixing the kit, it depends on what you want to do. In all cases, you
must understand that IT IS THE MIDI NOTE WHICH CONTROL THE VOLUME OF THE
SOUND. From Cakewalk, select the note and decrease its volume. Another
method is to change the volume of the midi source you used to record this
notes. From the DTXpress you must be carefull of your trig
settings(->minimum velocity and gain) and the volume of each pads, because
it can change the volume of the note.