I am not a pro but have learned that in most combination gas furnace/ air conditioners the air flow is sized to keep the heated air way down at a very safe level so that a child would not get the mildest burn from touching a register. This faster air flow is then not “ideal” during air conditioning season to remove as much humidity from the house air. Comfortable summer air inside the house is not just low temperature, low humidity is a big part of comfort. If you blow too much air through the evaporator the air does not get close enough to the “dew point” to maximize de-humidization. This is why many units have a relay that switches the blower motor to a lower rpm when the AC is running. This is also why you need to make sure the drain lines stay unclogged from mold.

The shutters on all the registers at the ends of the ducts of a 2 story or very spread out house ideally would be adjusted when switching from heating season to cooling season.
You cannot avoid the “hot air rises and cool air sinks” differences.

Two story houses create such differences that a separate AC for each floor makes sense even at added cost ( plus if one AC fails you sleep in the other cooled zone temporarily).

Buying a little hand held wind gauge like the “Kestrel” or its cheap knockoffs can be very useful to adjust registers, and it is not a bad idea to make “air measuring hood” out of a cardboard box to channel the air so that the wind gauge has an even flow to measure, instead of having to guess how to sweep the guage continuously over different sized openings.

It is very common for the return air ducts to the suction side of the air blower to be too small. A “choked” situation at the suction dramatically lessens air flow output of a wheel fan. It is also easy to miss that each little cross connection on the wheel is actually a tiny airplane wing that is very sensitive to dust building up on its underside. It is tedious to scrape clean the wheel wings but it can make a big difference. Most owners do not realize that is a hidden reason why there is an air filter - to protect the little wing undersides. Dust ruins the wing performance justlike ice on airplane wings can cause the plane to fall out of the sky.