Here is the wifes 400EX jetting.
MJ=170
Needle clip one position down from std. setting.
That was jetting for 500 ft. elevation and sand dune running.
I should have went one size larger PJ in it but it's such a PITA to work on that I left it OEM pilot and 3 turns out on the fuel screw.
You asked about the fuel screw. [ air screw on 2 strokes ]. On four stroke FCR carbs [ and CVK models ] the in [ CW ] direction reduces fuel for cold starting and idle to just off idle running. It does have influence throughout the zero to full throttle but just off idle it becomes very minimal. Adjusting out [ CCW ] enriches the starting and idle to off idle condition.
Most standard settings are 2 1/2 out from lightly seated. That is a baseline.
Going in or out until you feel a slight acceleration in RPM's and a smoother idle is a base way to try to get a good point. If you are having cold starts that take longer than normal cranking or longer than should be to warm up try adjusting the fuel screw out [ CCW ].
If you have to go more than 3 turns out to get proper fueling and starting that is indication to move to the next larger PJ.
For reference, 2 stroke carbs are the opposite effects and control air going to the primary system. In direction will reduce air, out increase air.
Hope that helps.