It's sad that this is what womanhood is reduced to for Jazz, cosplaying and dressing up. I'm sure this is the only reason he "decided" he wanted to be a woman, that his sister got to be princess and fairy and he wanted that so, when he was told "but you're a boy!" and they he, innocently, he said "then I wanna be a girl".
It's even sadder that Jazz is only happy when he's dressing up as "girl" or doing performative girly things. That seems to be the only moments when he's not indulging in food. He likes to do pseudo artistic things that he thinks he couldn't do as a guy. Seriously, I'm sure he'd feel great if he could just step out of the house dressed like a mermaid princess or something like it, rather than just wearing normal plain women's clothes. He never wanted to transition into a girl, but into a fairy mermaid princess.