He’s a product of his culture. When Dany teaches him to make love differently, he’s fine with that. He’d just never done it that way before.
Mostly Drogo is a placeholder: husband, warlord, savage. When Dany is threatened by the wine merchant’s assasination attempt, though, he comes through with a career-making (for Momoa) moment. This scene where he proclaims he’ll fight for the Iron Throne is astonishing and powerful. Don’t cross Drogo. Something he cared little about will now drive him completely. Family, tribe, love. This is his hierarchy, his core. Threaten them and you’ve called forth the fire.
And then he’s dead. Whatever hint of character we got is now over. He’s big, he’s a leader, and he’s decisive. The Enneagram options are numerous, and we have no more information to glean. I could assign a number to him on the assumption that he’s drawn from choices made in the novel, but I don’t like that. The show must stand on its own feet.