You can’t be fine to tune the carbs until both carbs are flowing the same amount of air at idle. You will never get it right.
You need a Unisync. You can find them on Amazon for pretty cheap.
Then you need a plastic (or aluminum if you prefer) carb hat.
You put a hole in the carb hat and seal the unisync to the hat.
Get the engine warm and idling at the speed you want. Unhook the throttle linkage so that the carbs are not hooked together.
Out the unisync on the carb, whichever one you want and adjust the airflow on the meter so the float in the tube is centered or close to it. Note exactly where it is.
Put the unisync on the other carb and read the meter. If it’s higher than the other carb, you need to close the throttle on that carb until it’s close.
Then go back and fourth between the carbs until the idle speed is what you want and both carbs are reading the same airflow on the meter.
Then you can hook the throttle linkage up and don’t touch the curb idle screws. Make the linkage hook to the carb, not the other way around.
The you can work with your air/fuel mixture screws.