1968 gts avs carburetor

It's not right or wrong, they control different things.
The lowest ones control the 'emulsified' fuel to the idle ports.
IIRC the single air bleed valve controls the air bled into the fuel to the transfer ports and the idle ports.
Most Carters use a second air and second idle restrictor. Would need to review the circuits on that carb before saying exactly what and where that air bleed restriction controls.

I guess the question is why you feel the need to mess with the mix screws?
Read the manuals and booklets carefully - some of those may be staked to limit their movement to far in our out. Read up on all that before forcing it.