Regarding yeast - instant yeast does not require proofing and works better at a variety of temps than dry active yeast. I use instant yeast because I can buy it by the pound and is therefore cheaper. I've know people who use dry active yeast and do not proof it - the proofing process is just to reassure you that the yeast has not died. Instant yeast can be added with dry ingredients (according to the package and to the book "Baking with Julia"), but I generally dissolve it in water first anyway. Instant yeast was developed in France in the 1960's and has only recently been available to home bakers and is more resistant to damage from high temperature. BTW, I would only use filtered tap water.
Once I made a pizza in Mexico City and forgot to take the altitude into account, and the dough rose all over the place! It was like the episode of I Love Lucy when she and Ethyl decide to bake their own bread! It still tasted good, and at the time, it was difficult to get good pizza in Mexico City. When I lived in Austin, much of the pizza had way too much Mexican influence and way too much cornmeal. I use no cornmeal, and to make a chewier texture, I substitute semolina flour for the cornmeal. I also use semolina flour on the pizza peel instead of cornmeal, and it works just as well.