Miller A storms are typically a single low pressure that develops in the gulf and heads toward the NE. The 93 Super storm is an example of a Miller A low pressure. These storms tend to have a narrow ptype transition zone and generally are rain or snow versus having freezing rain/sleet.
Miller B low pressures are the more complex of the 2. They feature a primary low that moves into the Tn Valley and begins to occlude over this area. This can also happen as a clipper systems moves into this area. As the primary low occludes the secondary low starts to take shape along the coastal front on the Carolina coast. This surface low becomes the primary low as it heads northeast. Miller B systems often lead toward messy precipitation transition zones as warm noses occur aloft.