Q1 - Lots. Costar of the film, outsized role given to her, she's in just about every scene that does not involve military stuff. I'd say its about 50/50 military drama/relationship drama.

Q2 - Yes-ish? Vanessa Kirby is good, and the role is within her usual range. Even if her period style and flexible idea of what a good wife is turns you off, you can believe that Napoleon is into her. Later in the film she becomes a much more sympathetic character. I would say the major problem from her perspective is that her role is all about and centered on Napoleon. It's not exactly a complaint, since that's basically her claim to fame and point of interest, but the film does not do a lot to give us an impression of who she is as a person, beyond the image that enticed him. As I noted in the review, there is NOTHING about her relationships with her children. Her son, as a child has a scene where he goes to Napoleon to ask a favor, which leads to their meeting, and her daughter has all her dialogue in a conversation with Napoleon after her death. Her maid seems to be a more significant character than her children. So even if you like the picture the movie paints of her, it's awfully two dimensional.

Fun? It depends on what you find fun. I think it could have been but the historical shortcomings and the grotesque aesthetic precluded that for me. There is a lot of Napoleon and Josephine acting silly and childish and gross in their mutual infatuation, and in the early scenes she seems to be playing a precursor to Fantine. Napoleon is more dour (because Phoeni, but also childish and childishly petulant at times.

But yes, the grotesque stuff and the OTT liberties they take with the history have a little bit of The Favourite vibe in there. But it's not the same type of movie, which told a personal story through the weirdness, while the weirdness in Napoleon seems more about demythologizing him or hanging negative symbolism and imagery on him.