Hi Tim
I am NOT affiliated with Villex electronics in any way (only as their most demanding customer probably), but I think I can answer the questions
1) There is only ONE (1) mid-control per pickup set (let it be 1, 2 or 3!!! Villex pickups on the instrument). But that mid control works in every pickup selection. The concentric vol/vol, mid, tone is a very useful outlay of controls.
2) The output of Villex pickups compares to the output of an active preamp (but no battery involved

). The output along with the tonal pallete offered made me remove the preamps from all Villex loaded basses of mine.
The most usedful addition to the above mentioned configuration was the addition of the PRTB (replacing the tone pot). The StellarTone allows for fine-tuning the tone pot function, while the PRTB removes highs and boosts lows and low-mids
http://www.villex.com/images/booster_graph.gif
Thing of the "basic" Villex tonal pallete (quite extended) expanded 4 times.
I do not live on the hype of graphs and internet; I use my ears and the PRTB delivers!!!


YMMV etc