How are the results in pizza baking different between one baking steel using a broiler, versus baking the pizza on a lower steel with a second steel on a higher rack? Is one easier to control (less likely to burn the cheese or crust)? Does a second steel above the pizza do a good job at cooking the top? Does anyone have experience with that?
I would say that in most cases neither is that helpful. I have great success with one steel, placed at the highest possible elevation in the oven. Preheat for at least an hour, and allow the steel to recover for a few minutes after removing the completed pizza, and before adding the next one. I have found minimal to no improvement with a steel or stone above the pizza. Also, in my oven, turning the broiler on, means the heating from the bottom goes off. I also need to keep the oven door slightly ajar when the broiler is on, so I lose a lot of heat this way. I find I don't need the broiler with my set-up. It is less convenient for marginal gains.
I cannot check to make sure this is the correct video (at work), But one of Adam Raguseas many videos on pizza goes over this in detail. It depends on what your end goal pizza is (Chicago/New York/Detroit/Saint Louis) and also what your preference is. All the methods you describe work, but do not drastically change the what your pizza is like.
EDIT: i was misinformed about the video had, but will leave it because it is a helpful resource.
from my comment below:
I think he must have gone over steel vs stone vs cast iron and not touched on that. apologies! In my experience, cooking under the broiler will burn food faster that just the steel. In theory the steel should only radiate the temperature your oven is set too, while the broiler will get much hotter. I think you need to consider how thick you pizza is to get a proper answer. More heat for thinner pizzas (broil) and then for thicker pizzas, the two pizza steels method you described should perform better.