I've seen professional cake makers bake a thick, 3" - 4" cake and split them, instead of baking multiple layers in separate pans. Might someone know any guidelines on adjusting baking time/temperature so I may do the same with my own recipes? I'm concerned with the outside being overdone, and the inside collapsing. Thank you!

I thought almost everyone makes 2" tall layers and splits them.  Does't take any special adjustments.  3" just bakes longer and possible slightly lower temp.  Really, just experiment with your recipes.