Gender plays a deterministic role in the world of Northanger Abbey. Well, gender itself isn't magically determining things. Expectations that are influenced by gender are, however. The expectations surrounding gender influence everything from modes of behavior to reading habits. And these expectations produce definite results – to a point at least. The characters here frequently disrupt gender expectations: Eleanor reads history books, Henry knows about fashion, Catherine doesn't keep a journal like "most" ladies do. Gender definitely determines and structures the world in which these characters live, but gender roles and traits are also up for debate in this text.
Though Henry often makes fun of women, or at least society's, ideas about what women should do, he actually has fairly progressive views on gender.
Henry is being serious when he makes fun of women and thinks that he is better than them.