Gee... Do the guitar guys not play with their pole pieces?
I do, I do! It's a bass, but the idea is the same.
The pic above is from when the bass was brand spanking new, so it hasn't been adjusted yet. These pickups get set a bit lower than those on other basses.
I start by setting overall pickup height in the usual way. This allows me to get the tone and
overall volume I want. Once I've got the body of the pickup where I want it, I fine tune individual strings using the pole piece adjusters. It really doesn't take much height difference to make a discernible difference in the sound, so small adjustments are the order of the day.
Also: Many of the MFD pickups have wax potting that appears to seal the pole piece adjusters in place. The fact is that it does this very effectively. So on a new instrument, turn the adjuster IN about a half turn before trying to turn it out. Make sure that the allen wrench is well-engaged in the pole piece, as the wax can impair insertion.
Ken...