It's not the speed of the pan, it's fine, it's that it responds in coarsely granular steps. On MacOS when you pan or zoom it updates at some rate, regardless of how much you move, so it feels smooth and fluid. On Linux you pan and nothing happens until you've panned a certain distance, then it skips over. It's as if the pan is locked onto a grid. On MacOS if I pan a tiny amount it moves a tiny amount. On Linux nothing happens until it exceeds some threshold, then it does a coarse skip, like there's a minimum panning distance.