OG5 Headcanon: The kids all have their own fighting style.
Ladybug: Half improvise, half overthink.
She doesn't know any specific martial art, but common sense gets you far. Firm feet to maintain balance, "I wouldn't want to get hit there, so I'll hit there", "If their attack doesn't connect, they won't hurt me", etc. She's VERY aware of the tools at her disposal, what she can do with them, and the environment, which is why she makes such good use of the yo-yo.
Chat Noir: He knows enough to be efficient while being unorthodox.
Adrien is free as Chat Noir, and he brings that freedom to his more chaotic and unconventional fighting style. He has a solid foundation in martial arts to build his own style while also making it functional—an improvisation with a more practical approach, so to speak. We also see him constantly making the most of his fencing skills.
Rena Rouge: She's going to kick your ass.
Alya is the sister of a professional kickboxer, so she's learned a thing or two from Nora, whether directly or indirectly. She's also a superhero nerd, so you're definitely going to get hit by a Superman Punch or a Raider Kick. As a bonus, she has three sisters and actively looks after two of them, both of whom are quite mischievous. She knows how to handle multiple opponents at once and how to protect her team.
Queen Bee: Elegance above all else.
Her eight years of ballet training are evident, kicks and pirouettes are the main menu. She's also very good at talking trash to provoke villains, whether to distract them, make them lose their composure, or simply because the blonde was having a bad day. As Ladybug's number one fan, she's obviously going to emulate her heroine's tricks, especially with having similar weapons.
Carapace: Smooth moves.
Yes, I know, the DJ knows how to breakdance, very cliche, I know! But I don't have anything else to work with. Literally his debut was against a boxing spider, and Ladybug was the one who fought, not him! Also his power literally makes him more defensive and support, but that doesn't mean he doesn't know how to do the Captain America's trick or how to move when necessary. Also a spinning kick to the leg WILL hurt.