Couple questions ... Idle screw, fine-tuning

Got my first build running CHERRY!!! had issues all along the way and just kept trudging through em. Now everything is perfect. No leaks, no rattling, no broken carb float! My question is at what idle speed is the engine at top performance. My bike is idling perfect I actually had to turn the motor speed down using the idle screw. Is it best to have it right above stall speed when clutch is disengaged? Little faster? Also now with good fuel, air, an spark is there anything simple I can do to fine-tune it? Been looking t upgrades but only found a couple that didn't relate to mine (drilling .040 hole in carb to help idle) definately wanna get an epansion chamber but I'm thinking my carb is allright. Air filter recommended after exhaust?
Thanks in advance.

Anks that's a good tip. Big problems last night though. Went to show it off to the fam cause it was finally running really good. Lost the idle screw on the way over. That sucks. I thought that was for motor speed but I guess it's the air mixture screw. So while I thought I was turning the speed down I was actually letting more air in and makng it rev higher(?is that correct? More air higher rev?) I think that was why I didn't notice any change when I was slowly turning it left. It was already running on full air. Can wait to see how it's gonna run now I know it needed less air. It already seemed perfect. Ordering a new scre off the Internet. Anyone know if I can find those at a hardware store or small motor shop?