Regarding the center pickup. I usually don't use them or even like them, especially if the output is lower than the humbuckers. On my Charvel, this is not the case.
I don't know which coils are used in each position, but I do know that on my GG, it's wired so that single coil is never the only only coil. This means there is no volume drop on any of the positions that use it, nor is there an increase in noise. The end result is that I actually use it sometimes.
That said, Charvel and GG are always making changes and mine is a couple years old. I don't know about the latest models.