I use 17.3” screen touch. Karma is an excellent software for touch - ONLY if you have 15 - 18 singers. The buttons are larger & easier to tap with your fingers. Once the rotation gets larger you have no choice but to adjust the interface to smaller fonts to accommodate more singers’ name in the rotation column; hence the buttons get smaller as well.
You now have smaller touch targets that are harder to tap without affecting the left or the right buttons. That’s when I switch to mouse.