I've been reading this thread off and on, and it seems to be running around in circles. I'll just add my 2 bits.
A standard hull is going to have crap poking out all over it. Turrets, sensors clusters, antennae, cooling fins, duct tape, whatever. It is not designed for high-speed atmospheric flight and maneuvering. The antigrav system provides lift, but not drive. Drive comes from the thrusters. Lift-and-drive systems in the vehicle book simply reflect glomming the two together. The drive system can provide limited amounts of off-axis thrust, but only at the expense of forward speed. So it can vector, but that slows it down. Without continual thrust, the barely-streamlined shape and afore-mentioned crap will slow it down rapidly.
In order to land, it slows to a near stop, and then starts cutting power to the lifters until it touches down. To take off, it just applies power to the lifters until it is clear to use the thruster. Big ships may need the cradles and pads to support their mass for long periods of time while grounded.
A streamlined vessel represents a boat optimized for atmospheric flight, with streamlined turrets, or jack turrets, and smooth lines. Control surfaces help it maneuver in atmosphere without relying on the limited vectoring abilities of the grav drive, though it can still make use of those, too. such a vessel is not like an airplane, though it may resemble one.