2 Questions
 

1. Is having 3 pick-ups really worthwhile?

2. How great of a difference is there from placing the neck pick-up REAL close to the end of the neck or back from it 2-3 inches. I don't know if there really IS a "sweet" spot for placement at neck OR bridge.

1. I have never cared for 3 pickup basses, both sonically and aesthetically.

2. The closer you move the pickup towards the center of the string, the darker the sound will get, because the strings move in a longer path. So 2 or 3 inches will make a huge difference.

Placing pickups right at the butt of the neck was popular back in the 60's. These were usually humbuckers and generally referred to as 'mudbuckers'. But the reason for that was that the amps of the day didn't really deliver much low end, so the mudbucker (with flat strings) was the work around to get some thump. In the late, 60s solid state power supplies became available and amps could suddenly deliver the low end like never before. And they did. And they did it some more. So much so that the amps became the mudbuckets and round strings came to be the work around for that. Today, amplification is sophisticated enough to handle about anything you throw at it.
A pickup right against the neck is going to be muddy and thumpy in the low position, but brighter than a bridge pickup at the top of the fingerboard. Depending on the pickup, this could be a desirable feature for a soloist. But I would want some serious input from a pickup guru first.

Thank you