You're welcome.

In the above context, I was referring to the relationship of the two coils of the trembucker. However, either can facilitate your purposes.

To answer your other questions:
The slug coil is always the more powerful of the two. However, the screw coil is always facing the extremes. Meaning, closest to the neck or closest to the bridge (respectively) and therefore, you'll get a touch more frequency response.

The "quack" will be more intense using only one coil of either of the outer HBs, wired in parallel.

Premising the middle pickup isn't HB on its own, this single coil would have to be RW/RP to the chosen single coil of both HBs. It is not enough to reverse leads with the HB, the two pickups' polarity would have to be opposite as well. Otherwise, the two coils would simply be out of phase with each other.