Believe me on this one, I have been on the receiving end to many times for my own comfort. A straight battle line is a good battle line. A straight line gives a morale block to the regiments in line. A morale block can be added for each flank covered left, right and rear and helps eliminate flanking fire as well. The flank is the key to victory in SMG if you can flank an enemy regiment the battle is half won.
Nothing beats a good flanking maneuver to really hammer an opponent.
Artillery is for me the biggest enigma on the battlefield. I have had my batteries wipe out an entire regiment with one volley, ah what a beautiful site it was, and I've seen them hammer away at a regiment with out doing a single morale block of damage. As best I can tell only three things really affect the damage artillery does. The closer the better. Nothing like a good canister shot to break up an attack.