When quickly scrolling up and down using two-finger-touch on mac I see > 120hz repaint rate (max I observed was 126).

Ideally you want a scrolling matching refresh rate; although doing it in excess of refresh rate can reduce input lag (lag between touchscreen and screen response) because even at 60 Hz, the frames are rendered 1/120sec before the refresh, rather than 1/60sec before the refresh. A savings of up to 8 milliseconds of input lag can occur when redrawing at much faster than the refresh; which can be important for touchscreen response.

(rationale - one 1/60sec refresh is 16.7ms refresh, and half that is 8ms)