but if they are manipulating gravity they would not feel it as a 90 degree sudden turn.
Cancelling cancels inertia? Are you sure about that? A craft if so arranged that it is an internal inertial system to itself will be ‘immune’ to gravity since gravity and inertia are so closely related.
I’m guessing they fly in something like an ‘other gravity tube’... the tube is rotated so for occupants every direction is straight ahead. It would also answer why there’s no sound - and no ‘wave of energy’ that moves tree limbs, air or causes drag.