It's definitely unresponsive. Very unresponsive. Also there's a very noticeable difference when I set both displays to 60hz. So it's unfortunately not the realization that 60hz is shitty compared to 144hz.
I don't have a iGPU, but I couldnt use it anyway, because I use the 1440p for work where I need the cuda cores of the nvidia GPU. (mainly Adobe stuff, quite a difference to non-cuda)