HC can wheel and move faster, but cannot about face. Light Infantry and Light Cavalry can wheel freely and about face. This makes armies with a lot of heavy units much, much less maneuverable than armies with a lot of light units. I played and lost, I could attribute my defeat to one or two wrong decisions. Decision making assumes critical levels since, much like initial deployment, recovery from a bad decision is very difficult.
Most units fight two ranks deep.
Heavy Infantry units have the most variety in possible formations. Typically, pike units are deployed four ranks deep. Deeper units are also more maneuverable. Also, units cannot change their deployment during the battle. How wide and deep you fight your HI is pretty dependent upon the enemy you face and how your battle plan.