There are moments in historic warfare, where commanders leave their logistic supply chain, and operate without resupply. What they gain is they move faster. What they loose is resupply.
The hope is that with an imminent combat victory you capture your enemies supplies, and feed and equip your army.
The risk is you don't win a battle and don't resupply. Suddenly your going to starve, and need to win a battle now. You enter a battle not because its tactically sound, but because you have no choice.
If your eating the soldiers you kill, capture, or your own wounded. Making the decision to go without your baggage train is a lot easier, because you resupplied off the battlefield dead. It means that you can break off from your supply lines, with more certainty that combat victory will 100% resupply you.
How might he best leverage his troop's culinary predilections to that end?
I would expect that an Orc Commanders are more aggressive in their willingness to leave their resupply lines, knowing they will eat the enemy post battle.
They would be more aggressively seek battle to maintain resupply.
I would expect that a Human Commander are less aggressive in their willingness to leave their resupply lines, knowing that Orc don't carry as much supplies and rely on combat casualties for resupply.
They would avoid combat until the Orc army is desperate for resupply, offer up a battle on unfavorable terms to the Orcs, and exploit your advantage to win.
Would it make much of a difference to his campaign plans?
If the enemy know about this, they probably prepared in some way (scorched earth, poisons, baiting them as above, predict the Orc will move quickly).
I am not sure that eating battle casualties will be much different from eating the enemies supplies in the real world.
Its hard to see its game changing, particularity if its common knowledge and the opposition adapt around this strength.