#2
Anything. It's just a tonal difference, like styles of bridges, different woods, and scale length. It doesn't really have one specific style of music, it's just a difference.
#3
Chambered guitars are lighter and somewhat brighter toned. Their sustain is minimally effected due to it being chambered in comparsion to a solidbody.

Usually they are used for clean stuff but a chambered Les Paul wouldn't have any trouble doing metal.
Major of 7 String Legion 7 > 6

Carvin DC747
Ibanez RG2228
Schecter Avenger Custom Shop
and my baby....
Gibson Explorer Studio