right, thicker caps will sound deeper and lower-pitched.

in general, sound profile is affected by a lot of things. here are the extensive listings: http://blacksimon.tv/science (alt: https://docs.google.com/spreadsheets/d/15Xm...0oqr8Aux24SNz0/ )

in terms of key caps, we can look at the keycaps tab.
you can try contacting builders at mymkb mechmarket's provider list, https://www.facebook.com/groups/MYMECHMARKE...79389625627322/

usually, a non-permanent fix would be to blow dry air into inside of switch using blower, and spam the keys repeatedly. this often works for mx style switches.