I live in Florida and we do have hot summers. I have had my coops under shade with shade in the birds runs. On really hot days I put a wading pool out and the birds actually walk around in the water. I have put misters out too for them. I moved my coops to a new location where there is limited shade so I will be building them shaded areas. My coops are all well ventilated. The coops are also raised up off of the ground.
Here are pictures of the inside of one of the coops just after it was built. - These are the vents on one of the other coops
Last summer was my first with chickens. I placed a box fan on the outside of the wired window pulling the air thru the coop--thru the open door and other window. I placed shade cloth over the top of the run and placed large plastic tub tops (2-3 inches deep) full of waterin the deepest parts of shade --I would find them walking, sitting or standing in it. Mid day of those 100*+ days, I would spray the run with water--not to soak it just to cool everything down.. I have all heavy breeds--BO, RIR, BR, EE and Ameraucanas. They did not seem to suffer too much/.
I'm in Florida as well. So long as they have plentiful fresh water and shade I haven't found any breed that can't take the heat and humidity. If I had to go for absolute best I'd go with White Leghorns because they'll lay when nothing else will. For brown egg breeds Rhode Island Reds, Barred Rocks or Sex Links have all worked well for me. Even my Black Jersey Giants learn to tolerate the climate and perform.