Forget about plugs when checking the idle speed/slow jets. And engine speed is a second order effect.
Wrap some tape around the throttle/body and use a sharpie to mark 1/8, 1/4, 1/2 3/4 and full and put a small piece of tape with mark on it as an indicator.
Starting from cold should require choke.enricher, so just get it started and get it warm. Air screw should be between about 3/4 turn out and 1 3/4 turns out. If it works better with the air screw further out, the pilot jet is too large.
Once you get it to idle, find a nice long road with slight hill and ride it wide open up that hill and do a plug chop. Do not ride home with the same plugs in. Take the plugs out and examine them or swap in a spare set and take those home to examine them in safety.
For main jet you want the center insulator to be white. Mixture you read where the insulator meets the shell. Look for signs of pepper spots (detonation) or cement boil which are signs of overheating from lean mixture, wrong plugs or too much ignition advance.
Once you get those dialled in, try 1/2 throttle to 3/24 and move the needles up or down to change mixture strength there.