It's largely the same as the movie. The big difference would be the battle outside Minas tirith, the battle gets glossed over when the boats arrive with a regular army. He probably didn't kill an elephant singlehandedly.
Sniper Legolas would make some things easier, hunting the uruks would end with them all being shot well before fangorn. If he had infinite ammo, he probably would have taken out a huge chunk of orcs at helms deep before the seige.