I have no idea what the mouse stuff is about or if it makes any diff
I also have 400dpi but instead of using a mouse pad I use sheets of A4 paper
It enables you to smoothly slide mouse and slower your rate. I know some ppl use a desk, I did try this but it was too sensitive for me. I guess it depends what your used to.
I play mostly on 1.16 and find some servers will have an effect on the mouse, it's strange but maybe thats just settings I have with different mod configs and they dont get updated when I change server. Sometimes you have to do in_restart ? to reset some changes.
I dont think any mouse dpi above 800 would make a difference in normal play unless your using zoom stuff, which I dont. If lag stuff starts happening on higher spec mice then I think I'll avoid em.
btw.. I dont know if this will help but if you goto a noghost server, there are some on 1.32 and see how the movement feels there. Most have pmove_fixed off and use pmove_accurate instead. This calculates the physics not by the clients fps, but uses the CPU to calculate movement. You see this on the lagometer when turning on/off pmove_fixed on the server. Playing with 60 fps will still give you the same movement as someone with 125 fps. Fair for everyone but I also find the movment feels so much better to control on vq3 and slightly different
I like TDM and pmove_accurate so I guess thats why im mostly on 1.16.