
external, internal, or both. The climax's job is to resolve the conflict(s) positively or negatively.
So-far-so-narrative arc 101.
The climax comes closer to the end of the narrative than to the beginning or the middle. "The Tell-Tale Heart" by Edgar Allan Poe ends with the climax. Die Hard's climax occurs approximately five minutes before the end (Sgt. Powell's climax occurs about sixty seconds before the end). The climax of Return of the King occurs nearly 1/2 hour before the end (of a 6-hour story).

In contrast, in many romances, the physical climax will precede the emotional climax. That is, Darcy will rush off to rescue Elizabeth's reputation, THEN realize that "oh, maybe, this means I should act on my feelings." In the manhwa U Don't Know Me, Seyun's external action--when he climbs the mountain with his friend Sun Choi and hears about his unrequited romance--precedes his internal emotional resolution. He returns to his lover--and the parents-in-law who adore him--ready to give up his I-must-do-everything-alone mindset.
On the other hand, in Beauty & the Beast, the physical climax and the emotional climax correspond: Beauty realizes that she loves the Beast at the moment of his death, perhaps at the moment she confesses.
Whether it precedes or follows the external climax, self-revelation in romances is necessary before the couple can resolve its differences/understand its true intent.
Romances with an external climax but no conjoining emotional climax are . . . better than stories without climaxes at all. But still less than satisfying. These are stories where the hero and heroine get together only due to the physical pay-off (someone was rescued; someone was saved from the villain or villainess; someone inherited a great deal of money; someone ran into someone else at the subway).
There's a good reason Austen changed the original ending of Persuasion. In the original ending, the main characters are maneuvered into confessing their love. The possibility that it wouldn't happen at all is staggering.

So self-revelation makes for stronger romances--especially if the self-revelation corresponds to the external behavior/outcome.
That sounds obvious, but I occasionally read narrative essays by students where this doesn't happen: the climax fails to prove the thesis. If, for example, the thesis is that individuals are formed by free-will, but the story resolves with a character at the mercy of social forces, self-revelation and outcome have failed to correspond.
Fiction doesn't use thesis statements (and shouldn't) but the principle still holds. The character's inner resolution needs to match the character's external behavior (even if that doesn't happen in real life). If, for instance, Romeo decides that Juliet isn't worth the sacrifice--there are other fish in the sea--he's got to be given another reason to go to the church.
In the future, I will be posting various examples of different resolutions/pay-offs (good and bad). In the meantime . . .
Advice for Romance Writers: Make sure there is an inner emotional climax as well as an external physical one and make sure the two climaxes fit together.