I am building a 1560 sq ft home in South Texas

[Darnel]

It gets very Hot & Humid in my area. I was looking into Goodman 16 seer DSX 16 AC / 4-ton unit. I divided the number of sq ft by 400. Also, do you think a 5 ton unit would be best due to the Hot conditions where I live?
The Goodman has a Lifetime warranty on the Compressor which I feel is a Great Deal.

[Freon]

I would strongly suggest getting estimates as to sizing and cost for your HVAC system. The company that installs the AC will also do a thermal load calculation to make sure it's the right size. To me 5 tons seems big but your house may have no trees and full glass to the south... hence why you need a load calculation.

If the system is too big it will not run long enough to remove humidity. You'll have a cold humid house as a result. The best size is when the AC runs constantly on the almost hottest day (design day) and keeps the house at the set temperature.