Differences I would see in a female version of Luffy:

1) It could change the nature of the story to an extent. How certain characters would act around her, especially Sanji.

2) Changes to personality: Still goofy, childish, and fun-loving, but also shows a more thoughtful, mature, and even sophisticated side. Can also be cunning when dealing with enemies. Like a hint of Lelouch Lamprouge (Code Geass) and Ryuko Matoi (Kill la Kill) combined, with an appearance similar to Ai Hoshino (Oshi no ko).

3) I decided to give her new devil fruit abilities: Star-Star Fruit. The abilities include shooting star bolts from her hands, levitating, making force fields, and making little stars from her hands that float around in the air.