I tried what you suggested, but when I try to adjust screws on the carburetor, no matter which way I turn them there’s no change in rpm
Run half to 3/4 choke , if the rpm drops to "normal" either the jetting is too small or maybe a kink in the fuel line, or maybe the fuel shut off gasket is a bit wonky and its starving for fuel, or you just have yourself an Ole fashion intake leak allowing it to suck extra air where it shouldn't be and youll need to to find it.
It's also possible assuming it's the same engine they used on the mini bikes (Coleman CT200U-EX has a Hisun 196cc [Gx200 clone] engine)
that either the throttle cable is pulled too tight or dragging, or the throttle plate has the pivot too tight and it's sticking.
I swapped out the throttle plate due to not having a specific little spring that China figured it didn't need to pull the throttle plate itself back to idle. The return spring they put over the cable is far too weak to draw the cable fully back to idle and should be swapped for stiffer spring.