I like to think that Worf's stoicism reflected his impressions of older Klingon champions he idealized from the TOS era, who seemed split between the mercurial hammy characters that TNG and DS9 had and the more disciplined and colder professionals that you see in stuff like Star Trek VI - while Koloth was pretty in-line with the TNG Klingons, as were half the movie Klingons, guys like Kang, Chang, Gorkon, and the other half of movie Klingons had more dignity and control.
Not to say they couldn't be hammy as well, but they had the type of hamminess that Worf himself has - they flip the switch in combat or conflict after being surprisingly chill and controlled outside of it. Chang's all eerie calm and control when meeting Kirk and at dinner, then Plummer gets to let loose in the court room scene and in the battle, just like how Worf's the stoic, "unfunny" guy, and then is grinning and howling like a madman when getting a good fight.
Of course, it also pays to remember that Worf simply bases his "Klingon-ness" off second hand information when he's young - he's got the backstory of a second generation immigrant who idealizes his home culture without having first hand experience of it until after he's matured.