right type of electric box?

i see there are lots of electric box options and trying to figure out what type is best. whats the difference between a switch box and utility box and what one is allowed to be covered in drywall? also can an electric box have knockout clamps if covered by drywall? i am looking for an electric box thats metal, has internal nm clamps and can mount to a stud and at the same time can be up to 5 to 6 max gangs and low as one. some metal boxes have the screw hole outside the box as opposed to a utility boc where it is inside the box. are there long 6 gang boxes that mount to studs and have a plaster ring thats 5 to 6 gang? here is a link to what i am talking about except i want internal nm clamps and plaster ring: Shop Raco 63.5-cu in 4-Gang Metal New Work Wall Electrical Box at Lowes.com (http://www.lowes.com/pd_141545-427-687_0__?productId=3651798&Ntt=gang+box&pl=1¤tURL=%3FNtt%3Dgang%2Bbox%26page%3D2&facetInfo=)