I like having the pickup (both bobbins on a humbucker) adjusted closer to the strings as it allows more magnetic field from the string movement to cut through the coils to produce more current or output in a pickup. If the two bobbins on the humbucker are further away from the pickup and the pole pieces adjusted higher the pickup would give you less output and brighter sound. I like keeping the coils, magnetic field and strings close to make the pickup work more efficient with my playing style. The pickup is more sensitive when all components are working closer together. You can play real subtle or with lots of attack and overdrive the input stage to get more growl from the pickup.

Try looking at many makes of pickups, shapes of pole pieces and type magnetic fields they have. Gretsch used a pickup they called the “Dynosonic” and was made by DeArmond Pickups company back in the 50s and 60s. The pickup has adjustable 1/4″ diameter magnets and to get enough output out of the bridge pickup the pole pieces had to be adjusted really high. By doing this made the pickup sound slightly fuller but still not enough output to balance with the neck pickup. I like to build special shims to raise the whole pickup closer to the strings and leaving the poles adjusted lower in the pickup. I get better output and fuller sound that balances much better with the neck pickup.