With the way your second design looks, I would assume its a freighter, and those two left variants are it mounting different cargo units.
For the first design, I feel that those booms are a bit too substantial. I assume that they are some form of communications antennae to support controlling the drones. I would suggest either making them thinner, or add some kind of arrays to them to make their thickness necessary.
For your third design, that chin fin feels a bit too much. In my opinion it protrudes too far beneath the rest of the ship. My suggestions are to add some additional ventral bulk beneath aft of where the narrowing begins to balance it, or cant the ventral portions of the narrowing slightly upward so when it does protrude it doesn't extend as far beneath the hull.
Just my opinions. Feel free to disregard.