distance b/w pickup and strings

It definitely is down to your liking. For EMGs there is a rule though. As they don't have strong magnetism you should set them as close to your strings as you can. That will help you to get the sound you want. For passive pickups what I always do is I set them close my strings until I get distortion on my amp in clean channel. Then I set down until I get the sounds I want.
 
Commandante said basicly what I would have said. I use EMG's on all my "metal" guitars and for the fusion stuff I use passives. On all my guitars I set the action unusually high and use very heavy strings for greater volume, beefier tone and not to mention I just like to feel the strings as I play.