800 dpi is a medium sensitivity for gaming. Most professional players use their mouse at 800 dpi as it is the right balance between accuracy and movement speed. You can use your mouse at 800 dpi if you're not very familiar with high sensitivity.
Yes,1200 dpi is suitable for gaming. This may be seen as a little high dpi setting for the mouse as most of the professional players go for lower sensitivity. 1200 dpi might work for you if you want fast mouse movements in your game. It's always better to experiment until you find the right dpi setting that suits your playstyle.
There is no such thing as a correct mouse sensitivity. Mouse sensitivity depends on the task you're doing and your preferences. Some people prefer to use their arm to move the mouse so they will prefer a mouse with lower sensitivity whereas people who like to use their wrist for the mouse movement will generally prefer a high-sensitivity mouse. You can choose according to your requirements by experimenting with different sensitivities.
Low dpi is preferred for fps games because you need to make fewer movements and need to be very precise. Low dpi gives you consistency with your aim so that you get that headshot in every fight. Most of professional fps game players like CSGO or Valorant keep their dpi around 800. There can always be exceptions and you can try higher sensitivity if you are comfortable and that works for you.
Low dpi is preferred for fps games because you need to make fewer movements and need to be very precise. Low dpi gives you consistency with your aim so that you get that headshot in every fight. Most of professional fps game players like CSGO or Valorant keep their dpi around 800. There can always be exceptions and you can try higher sensitivity if you are comfortable and that works for you.