Type about:config in the url bar, press enter.
In the search field at the top of the presented window, type smooth. It will filter smooth related browser preferences.
In K-meleon 74, aren't only 2 but a few more:
You'll need to search at kb.mozillazine.com and other sites the exact meaning of them to know what to touch.
I know it isn't the answer you were searching for, but there isn't a simple method.