The amount of moisture that an a/c removes is adjustable to a point. The sensible and latent ratios are dependent on the moisture content of the air entering the cooling coil, amount of air flow through the coil, the coil temperature, and minutes of run time.
True that over-sized a/cs need more tuning to maintain specific temperatures and %RHs.
All a/cs over or undersized are unable to remove any moisture with out substantial sensible cooling loads. Evenings and rainy days require supplemental dehumidification to remove moisture during low/no sensible cooling loads and +50^F outdoor dew points.
A well sized a/c should may need to be slightly oversized if the being able to cool down capacity when occupants return to an unoccupied home, visitors are in the home, and the equipment ages.
The difference between meeting a customers expectations and unexceptable preformance is a fine line.
Keep in mind all sized a/cs in green grass are not going to maintain specific %RH without supplemental dehumidification, reheat or a small whole house dehumidifier.
Learning how to fine tune or setup the a/c is most important and understanding the role supplemental dehumidification in maintaining specific moisture levels in a home. Slowing sensible cooling and increasing moisture removal is part of the setup process.
This process is more difficult than jumping to the "it is an oversized a/c" problem as opposed to setting up the a/c and explaining the need for supplemental dehumidification during low/no sensible cooling loads and high outdoor dew points. Also consider, the moisture from the occupants and the need for minimal fresh air change during occupancy.
Comfort and preventing biologicals like mold and dust mites are part of a modern space conditioning package.
Keep us posted.
Regards Teddy Bear
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"