To compare to your home, I have a Florida home built in 2007 with a radiant barrier on all exterior walls and the attic roof is also lined with it. Windows are only single pane, amazingly the only code for windows in Florida is impact resistant. I have a 3.5 ton installed in 2015 Seer 16 Carrier Heat pump unit, one stage cool. Thermostat in the summer is usually set to 77, the power company recommends 78 degrees. The high outdoor temp is at 90 or higher everyday for about 3-4 months year, the AC runs often and it keeps the humidity in control. Right now at 10:00 am it is 85% outdoors, 54% indoors. It rarely gets below 50% in the summer. Come the cooler months without the AC running much the indoor humidity does get 60% or higher. My Smart Honeywell Thermostat sends an email high humidity alert from the Honeywell server. To drop the humidity I'll lower the thermostat to 75 or lower and in an hour or so the humidity is in the 50% range.
As Fitter suggest you can have leakage sucking in humidity, especially when the dry is pushing out 100 cu ft per minute and the replacement air has to come from somewhere. Did you have a humidity meter with your old system? With your stat set at 70 the indoor dew point drops making it harder to wring out moisture. Another cause it an oversized cooling capacity but having a two stage that runs at 70% of capacity in stage 1 (~25,000 BTU's) it cannot be know unless a heat load was calculated.
To keep humidity under better control, keep the stat the same throughout the day. If you increase the temp while your out of the home such as for work and then lower it when you get home, the humidity will remain high.
The cooling stages are controlled by the thermostat and in the manual for your model, stage two kicks in when the set and rom temperature is 2 degrees or higher, a common default setting for most thermostats. The statement from American Standard is not clear how the 70% is controlled. It's possible an outdoor temperature sensor is needed.
https://www.americanstandardair.com...ing/air-conditioners/gold-17-air-conditioner/
GOLD 17 CENTRAL AIR SYSTEM HIGHLIGHTS
- Reduce up to 56 percent of your energy usage with this central air system that surpasses government efficiency standards.*
- This home central air conditioner runs at 70 percent capacity except on the hottest days when it steps up to the second stage thanks to a two-step Duration™ compressor with two-stage cooling.