My army composition at the time of battle of Richmond (but I've been using the same composition essentially the whole game):
I corps:Elite Infantry corps. (holding the line and assault)
1st division - Elites of the elite.
All divisions except 1st division have one 10pdr cannon unit (workhorse cannon).
2 units of skirmishers per corps.
One or two units of cavalry per corps
These are my Triarii. I hold them back and if they don't see any fighting, it's a good battle.
II corps: Artilery corps (Assaulting and holding fortifications )
1st division - Elite infantry for this corps. Just infantry.
2nd divison - All heavy artillery. 20pdr parrot, 24pdr howitzer, one unit of whitworths.
Other divisions - Infantry with 10pdr cannon unit.
One unit of skirmishers per corps
One unit of ranged cavalry per corps.
III corps: Cavalry corps. Speed (quick reinforcements and exploitation)
1st division - Elite infantry for this corps. Infantry and 1 skirmisher
2nd division - Cavalry only. Mix of melee and ranged
Other divisions - Infantry + 1 cannon + 1-2 skirmishers.
IV, V corps: Infantry corps (fresh troops - assault and first line defense)
One cannon per division, 1 cavalry per corps, 2skirmishers per corps
additional units (ie. heavy cannon) may be assigned according to mission.
These brigades are deemed expendable if need be.
In my opinion, using this every corps is usable for every battle, but some are more good in some form of warfare then others.
Regarding first level infantry perk - I don't take the morale buff. I get high morale from my political points.