A really simple way to understand up B's remix is that all you have to do is hold X if you want to jump cancel out of it (forward, no directional input is necessary but you can hold up or forward if you want). If you want to jump backward then just hold down as you're holding X, that's easy enough. No direction is necessary after the jump comes out, just an A or B input if you want to do an attack that comes out with it.