This might be a silly question but it's something that's been bugging me for a few years now since I run that character, how feasible would it be for someone to dual wield two vastly different type of swords and try to bridge their styles together? Say, for example, a rapier and a scimitar or perhaps even a katana. This is in context of dark urban fantasy and a wielder that while somewhat around peak performance does not enter shounen protagonist territory and is focused on agility and speed
Very feasible, honestly, simply because style is never as strict as, say, games or media would like you to believe. A style of combat is, by definition, in constant flux, and is adaptable and flexible by necessity. Let me put it this way that’s been effective for me when it comes to explaining it to people on the internet: When you train martial arts, you’re learning passive abilities for the most part, not active abilities.
Muay Thai, MMA, Kickboxing, you name it, it is for the most part 1) physical conditioning and 2) mental conditioning. Do this, don’t do that, and drill your mind and body to react appropriately to the enemy while trying to think as many moves forward as possible to get that takedown or that kick right on their jaw or that joint lock, all of which are countered in a way you understand, so you fake your enemy out by doing this or that, or do that or this in order to get a quick leverage on your foe and prevent them from properly defending against what you have in mind. All of this is thought and actualized in seconds, because it’s muscle memory doing the talking mostly, not actual planning out like playing poker.
End of the day, a fighting style is “this works” first and foremost. The same is true for weaponry. There’s no such thing as incompatible weapons: Rapier and uchigatana? That means that you have good thrusts and an easily controlled, light weapon on one hand, and a primarily slashing, heavier weapon on the other. It does the opposite of limiting you, it expands your possible array of moves both offensively and defensively. Lots of woodland rangers, for example, would wield a long dagger and a hand axe precisely because of this: Axe can cut through leather and metal, dagger can stab through chain mail and cloth, they are short weapons easily used among trees, among other benefits.
More weapon = More effective basically all of the time as long as you’re not being ridiculous with what you can feasibly swing one handed (ridiculous = two bastard swords).