Hi! THANK YOU sooooo much for your question! When I do genderbending, I love to keep almost all things about a character the same except for what might change based on how other people would treat them regarding their gender (in both positive and negative ways). So for example, my fem!Usopp is more concerned with her physical appearance (building jewelry and wearing colorful fabrics) because she was raised mostly by herself after her Mom, Yassop, left and her Dad, Banchina, died and learned at an early age that girls get listened to when they look more pulled together, something that likely didn’t affect male Usopp since boys are allowed to be a bit more rough and tumble. Masc!Robin, on the other hand, had an easier time living on the run but he struggled to develop advanced social skills and is therefore a bit more standoffish and shy than canon!Robin (this is why he wears gloves when we first meet him in Girl Piece). I have more in-depth ideas about how fem!Zoro and fem!Sanji’s backstories/timeskip might change (because gender roles and expectations play a large part) but it’ll take me some time (and space) to fully write them down teehee. When I publish my fem!Zoro design, expect there to be basically an entire fanfic in the caption LOL
Admittedly, a lot of my design choices are aesthetic ones since I am primarily a visual artist so I have a lot to say about what the characters wear and how they perceive themselves. If you’re interested in how their behaviors and the story itself might change, I (once again and forever will continue to) recommend ~Well Hello Ladies~ by @kooabreen on AO3. Her work affects mine often and vice versa. She can take one of my half-formed ideas and run with it, turning a tiny little detail (that’s maybe 10 pixels wide in my art) into a beautiful chapter about sisterhood.