Option B has cooked more brisket and other things than one can imagine……it offers for very efficient air flow (ie including almost instant response to temp changes if you want). It has a nice mix of radiant heat with convection. Having a water pan just inside will temper the radiant when desired, but you have it when you want it…… let’s just say I’m a simplistic cooker
Just know your tank is just not that big to have huge issues one way or another, but adding restrictions into the system make it more temperamental…….the basic design is just a chimney of coals and the feed it 3 inch splits and needed…….
Another food for thought…… as a variation to “B” if you drop the FB lower and have a “stack” or chimney (rectangular) the same area the would be FB to CC opening so that the FB is lower, ie it will operate similar to the pipe design above but it will flow way better and turn it into a true convection cooker, but you loose the radiant…….its all personal preference in cooking……