Unfortunately, as grabbing is not structured like a normal power, there are some grab mysteries when attempting to suss out exactly how it interacts with different things.
Firstly, is a grab an attack?
Secondly, does CA apply to grabs?
Thirdly, if I grab with a garrote (which deals 1[W] damage on a success) can I apply sneak attack damage? (assuming I have the Garrote Training feat.)
Fourth, if I'm grabbing with a weapon, can I apply the proficiency bonus? (Note: The grab entry says you must have a free hand to grab, a garrote is a 2H weapon.)