I can feel the life draining out of me.
People often refer to mouse DPI. this stands for "dots per inch". However, what is a dot? it can be many things, like a printer dot, or a pixel on your screen. Right now your monitor is set at 96 DPI, or 96 pixels per inch. This has nothing to do with the mouse.
The new term that people should use, but don't because they're stubborn, is CPI, or counts per inch. The mouse takes a count, then compares it to the previous count to get movement. the higher the value (400 CPI vs 2000 CPI) the faster the mouse will move on the screen. One count at 6/11 windows mouse speed is equal to 1 pixel on the screen, thus how you get "DPI" from "CPI".
So then, if you are having trouble playing osu, it's not a problem with osu, and there is nothing the developers can do to fix your problem. What you need to do is buy a mousepad at staples or office depot for $3. Then you need to practice. You won't magically be as good when you switch hardware, since your hands are used to different sets of hardware, even if they're very similar.
You might also want to turn off vsync/ 120 fps frame limiter.
Personally I use 7/11 windows, 1600 CPI, and 1.8x osu multiplier. You can't change the CPI on your mouse (at least it's unlikely) but most of the time it should be set at the highest value possible if you can change it.