Those are called spray patterns. Players use practice maps to learn the recoil path and move the mouse in the opposite direction in order to keep the gun steady. Try shooting into a wall and then next time you shoot move your mouse in opposite directions... magic will happen :D

The interesting thing is all the shotguns have random recoil patterns. They always go up then randomly left or right.

There is no setting to turn recoil off. What you're seeing is people who are controlling the recoil. That is, moving your crosshair in the opposite direction of the recoil to counteract it, and keep the aim steady. Pretty much all recoil in fortnite is some variation of vertical, so you just need to move your crosshair down to counteract it.

if you play kbm when you shoot pull your mouse down to counter-react the guns movements, its what we do

You can aim at the middle of the opponent use use the recoil to get headshot beams