Some humbuckers work better than others. I'd speculate that the amount of bucking you're getting is related to the quality of the design. I had a
Fishman Rare Earth that was quiet, but it did sound like a magnetic pickup so I was never totally satisfied with the resultant sound.
Induced A.C. hum can be caused from a circuit running close by your area that is going to another part of your house, so not necessarily your computer setup.