On my system, one click of the scroll wheel on the mouse moves 3 lines. Kate seems to be scrolling based on 3 file-lines. Whereas something like Notepad++ in Windows scrolls 3 visible-lines (which might end up only being half of a single file-line, for example). This means that for really long lines with word wrap enabled, scrolling can be very jarring and not smooth, as half the screen could go by in one tick of the wheel.
Can Kate be configured to scroll by visible lines instead of file lines? Or is this actually a system setting somewhere, unrelated to Kate?