What it is:
Another fully adjustable parameter on an electric guitar is the distance/height of the pickups. Through the two screws on the sides, a pickup can be raised, lowered or inclinated.
What it does:
The distance of a pickup from the strings has a strong impact on the overall sound, on the balancement of the volume between low strings and high strings side and balancement of output between pickups.
A pickup set too close to the strings will typically have a higher output, a grittier and more compressed sound and a stronger magnetic pull; in other words, the guitar will be louder but also less dynamic (less faithful to the player’s touch), the sound will have more presence but the magnetic field generated by the pickup may create anomalies on the string obscillation (therefore, a sort of warble sound and intonation issues).
On the opposite side, a pickup sitting too low will sound quieter, very dynamic but too thin and sterile.
There is no such a thing like a “sweet spot” good for all the situations (as everyone has a very different touch and needs) and, as often happens, the manufacturer’s specs are, in the best case scenario, a good starting point.
A good trick is finding the best sound possible (according to the player’s taste) on at least one pickup. Once this is achieved, you will raise or lower the other pickups so that they have the same output as the first one. This will create an harmonic balance all across the pickups selection.