There is about 1 frame (16ms) of added lag in vWii mode compared to a real Wii.
It depends on the width of the game's output. If the width/2 is even, an odd-numbered offset (i.e. 1 or -1) will align the chroma better. If width/2 is odd, an even offset (i.e. 0) will be better. Melee has a width...