The sizing chart for the shirts seem to show the same dimensions for both types. What am I missing here?
Can you be more specific? Which two types?
I click on tee. Classic and fitted appear to be the same sizes.
Either way it will not matter. I am as broad through the shoulders and chest as through the hips. These don’t look like my kind of shirts.
Love the design though. 
For men’s, they are the same specs for the length and the underarm chest measurement, but they are cut differently
Not sure what that means. If someone is built like a boulder which one would be better? Classic or fitted?
The classic is your traditional tshirt. It has a loose fit. The sides are pretty much a straight line from the armpit to the botton.
A fitted tee will be tapered at chest and waist for a more form fitting shirt.