Re: Pot Values
The higher the pot value, the brighter the tone . . . to an extent. But the affect, at least to me, is subtle. I prefer the slightly more mellow tone of 250's on all my guitars, but then again, it depends a lot on your setup. I play through a mixing board, through studio monitors, so my setup leans towards being bright.
In an amp, with twin-12's, I might prefer 500's.
As for vol or tone for the PP, its all a matter of your preference. Whatever seems more natural to you. From an electrical point of view, it doesn't matter.