I have a Logitech mouse, and a 2560x1440 monitor with DPI scaling set to 125%.
I checked my Logitech DPI settings and the DEFAULT one I use after tweaking a bit is 1400dpi. With other games (probably due to different resolution) I use either 800DPI or 2000DPI.
I played also with the POLLING RATE but 125 felt the same as 1000 to me.