At Marineford, specifically in Episode 478, Luffy demonstrates he has no control over it. It fires off randomly when his emotions are at their peak.
Both versions depict Luffy using Conqueror's Haki. The anime simply dramatizes it for the viewer to ensure the significance isn't missed. luffy uses conqueror's haki marineford episode
As Portgas D. Ace faces imminent execution on the scaffold, the Marines prepare to carry out the sentence. With Whitebeard incapacitated by a sudden heart attack and the Whitebeard Pirates struggling to break through the Marine defense, Luffy’s desperation reaches its peak. In a raw scream to stop the executioners, he releases a wave of spiritual energy that ripples across the entire battlefield. Impact and Consequences The anime simply dramatizes it for the viewer
This episode has significant repercussions on the narrative, as Luffy's display of Conqueror's Haki: With Whitebeard incapacitated by a sudden heart attack