If you are building this thing like a fortress with super insulation and foam, you better find someone who knows how to size the A/C or you will have water dripping from the ceiling.
Example: friend had a 1700 sq ft 2 story (850 a floor) plus full basement. House was foamed including roof deck. Lots of windows, probably lots more than a townhouse with people on the sides. And exposure on both sides which even an end townhouse won't have. We get similar temps and humidity as NYC.
She did fine with a 2 ton. The 92% furnace was 60K 2 stage with 36K input on low. Each level was a zone. Furnace couldn't go to high without all 3 zones calling. She never turned on the basement stat. So this house heated below zero on 33,000 BTU output.
Dealers just don't know how to size a tight house. My friend the foamer who did this house, showed me an email from another customer who listened to their HVAC sub on sizing and now has humidity problems.