It is more important how is your gimbal construction, and how solid is your camera installation, than motors, though motors play a big role too, not the motors them selfs, but the bearings. If there is play on bearings, the gimbal will vibrate easily.
Also it is important that all axis move feely. otherwise there will be the kind of delay you are having, especially at low PID.
My advise would be try to make the gimbal more solid, remove any flex it might have. Your gimbal looks quite ok (difficult to say looking just from one angle), make sure though that the camera is firmly installed and can not move. How is the IMU installed? Also make sure there is no play on the motor bearings. When the gimbal is solid enough, you can raise the PID and it will perform much better.