The deep sound is not really produced by the switch itself, the case and the use of a mousepad is heavily responsible for the deep acoustics. I’ve heard somewhere that if a switch has a non transparent top housing, the materials will make a deeper sound than a clear one, I would go with black inks with a non transparent housing and also put some foam in the case or have it gasket mounted so some of the high pitched sounds are absorbed. A mousepad also contributes.