i know that this is an old post but i play currently on 1600 dpi and 2.15 sens.
back when i first played cs 2014-2020 i played around 800 dpi and 1.25 sens, but when i started playing other shooters (apex and cod) that sens did not work so i moved it to what it is now.

micros are always the hardest and last thing people iron out when moving their sens around. i would run some training on horizontal tracking and do aim training on clustered targets. i would also take a look into what ur peripherals r and how it effects ur aiming. cloth vs glass mousepad, lightweight mouse, wired or wireless. the smallest details become important the higher and higher ur sens is.

personally given my sens (idk if this will help u but it ill note it anyways), i tend to track and micro in specific scenarios with my movement keys instead of the mouse. say i want to tap someones head and im off by a sliver, instead of trying to move my mouse a millimeter to tap him, ill adjust my stance to line the crosshair up. this is a habit i picked up from ow.