The airscrew is the easiest to adjust, so you might as well experiment with that first. If it seems to work best at 2.5 or more turns out, go one leaner on the pilot jet.
You could also try putting the needle clip one groove higher, which drops the needle. Also easy to do and free.
Another thing that effects low/mid running is the cutaway of the carb slide. But buying a different slide or modifying the one you have is either costly (new slide) or non-reversable (modifying your old slide).
Finally, your bike has a small motor, old carb technology and it is tuned to run at high rpm (which it apparently does quite well). If the bog is not bad, you might already be jetted as good as it is going to get. If that's the case, abuse the clutch and keep the motor in an rpm range that is above the 'bog'. That's the way to ride an old school 125!