If you want custom voices/SFX on characters you should riivolution without file patch code. With Gecko, you have to use file patch code but doesnt support Custom SFX.
But i dont know how it works for configurable USB Loader.
usb loader you have to put the custom voices/SFX on characters you have to put it in the iso file and load the game through usb loader but for gecko os idk how to do it