Jazz bass pickups query, please help

TypicalJazz bass pickups the bridge is wider than the neck.

 

They are almost always RWRP.

 

No. Typically the bridge pickup has more wire on it, because of the extra length. This extra wire is equivalent to a slight overwind, and it is advantageous to balancing the outputs of each pickup, because at the bridge position, there is less string movement to be transduced.

 

This^

Sometimes both are the same length but the bridge is still often overwound for the above reasons. They are also reverse-wound and reverse polarity with respect to each other so as to act as a humbucker when both pickups are on full (talking about standard single coil jazz bass pickups here). If you were to reverse their positions on the bass (assuming you had equal length ones) The overwind in the neck position probably would not be noticed but the underwind in the bridge would make balance slightly off (less bright) when both pickups were on full. Probably not a big deal though.