FPS limit fine-tuning
Don't set cl_maxfps to 0. Define a limit, based on the power of your pc. The more the better, but you want a stable value, so you got to figure that number out. The number you choose must be related on your monitor's refresh rate. cl_maxfps can be equal, double, triple, 10 times the value of refreshrate. This usually delivers good results. Just don't set it too high, you want stable fps. Typical values on modern computers are 240 (120x2), 480, 600, 960... which should be more than enough to have a smooth playing experience.

Especially with LCD devices be aware if your FPS limit (cl_maxfps) is a multiplication of your display refresh frequency. For example using 75 Hz display refresh frequency and FPS limit 225 (= 3*75) will be significantly different from using 235 FPS.

Setting cl_maxfps to a value that is below your systems limit also lends cpu time to other processes. This alleviates problems with mouse responsiveness (mouse driver) and CPU spiking (other programs).

[edit]Vsync fine-tuning
While vertical synchronization introduces image lag and forces one to use lower FPS rates than possible with unlimited FPS, on some configurations when fine-tuned it gives much smoother gameplay than when turned off.

To toggle vsync on, type vid_vsync 1 and cl_maxfps 0 in the console. Now you need to determine what is your video lag and FPS. Type show vidlag and show fps; You should use new hud (scr_newhud 1) to have these counters visible. The goal is to have stable FPS equal to your display frequency (60 / 75 / 120 / 150 ...) while having the video lag as low as possible.

Start with setting cl_vsync_lag_fix 1. Your video lag might decrease now, but also FPS may decrease. This is where cl_vsync_lag_tweak comes into play. You have to find the lowest value of the _tweak variable that gives you stable FPS equal to the display frequency. Such a value will decrease the video lag as much as possible without breaking FPS stability. For example tweak set to 0 will decrease video lag to almost 0 ms, but most probably will shut down your FPS rate. And tweak 20 typically won't reduce video lag at all, even if your FPS is super-stable. So find some good value in between.

[edit]Mouse
Use in_mouse 3 (Raw Input), or if that doesn't work in_mouse 2 (Direct Input). Type in_restart to restart input mode.

The G402 is relatively new, and so should have a default USB polling rate of 1000 hz. No need to overclock your USB. That is mainly used for older Microsoft mice.

Most people use raw input because it circumvents any potential processing or acceleration that the OS might apply to the mouse signal. I would recommend using it.

The most important thing is to have a stable frame rate. Better to have a frame rate locked at, say, 200 fps than one that varies between 500 and 1000 fps.

Make sure VSYNC is off. It adds noticeable lag to the video signal.

If your "fine pc" has an AMD video card, beware that these cards have performance issues with QW. (I know because I have one). At the very least you will want to disable all standard dynamic lighting in the client (rocket lights, powerup glows, etc) and use simple lighting instead. Rikoll has uploaded configs optimized for AMD cards.

So what do we make it from here?

A simple formula that goes like this:

monitor Hz <= maxfps <= mouse Hz

While considering the stuff I already mentioned above.

Sync everything and you get smooth experience (125Hz monitor, 125fps, 125Hz mouse). Sync parts of it with very high refreshrates and you'll get smoother experience (150Hz monitor, 500fps, 500Hz mouse). To make it overkill, use very high refreshrates with slight desync (150Hz monitor, 13*77=1001fps, 1000Hz mouse).


EXAMPLES:

Entry level : 150Hz monitor, cl_physfps 77 + cl_maxfps 154, 500Hz mouse
Entry level + : 154Hz monitor, cl_physfps 77 + cl_maxfps 154, 500Hz mouse


In both cases, you can try setting the cl_maxfps to 231, 308, 385, 462, 539, and so on

Improvisation : 150Hz monitor, cl_physfps 77 + cl_maxfps 500, 500Hz mouse
Improvisation + : 150Hz monitor, cl_physfps 77 + cl_maxfps 1001, 1000Hz mouse


In these cases we are trying to maximize the effect of the mouserate by hitting maxfps to it or very close to it. Also notice that even if maxfps 500 isn't X * 77 it still feels really good. 13 * 77 = 1001fps with 1000Hz mouse is even better, if you can spot the differences that is (my guess here on differences would be: placebo).

What it says at the bottom about 1000hz mouse + 1001fps is definitely the best combination.

If you can't do 1001fps stable then try 770fps or 616fps. With a Geforce GTX 770 you should be able to get 770 or 1001fps solid if you have an Intel CPU... maybe less on AMD.

as said g402 can run at 1000hz natively without messing with usb ports

Is mouse DPI related to this also?
I mean, does it have any kind of math involved or should i go with what feel more confortable? ( g402 can go to 4000 dpi).

Try to use 2000 or less dpi on the G402. A small amount of smoothing is added to achieve 2080 and above (source)

Try to use 2000 or less dpi on the G402. A small amount of smoothing is added to achieve 2080 and above (source)

By any chance do you know which DPI's are native and which are Interpolated?

On the G400 it is only 800 and 3600dpi which are native and 3600 is problematic. I noticed a huge improvement once i dropped down to 800dpi but I am shopping around for a mouse now and I am considering either G400s or G402

The G400 is from the generation of optical mice that were variations on the Avago ADNS-3090 sensor, which doesn't offer many selectable settings at the sensor level. The G400s will be very similar in that regard as it shares the same fundamental architecture.

The G402 uses the more recent AM010 sensor (in conjunction with some kind of gyro/accelerometer which takes over tracking at speeds >~2.7m/s) which is configured to natively support steps of 80 CPI from 240-4000 in this mouse. Straight out of the box without drivers, the selectable steps are 400/800/1600/3200, all of which are generated by the sensor and not scaled by the MCU or through the driver software.