I do 3D modeling and animation. I do not draw.
But – I have been experimenting with the Wacom Bluetooth stylus on my iPad.
The iPad and similar Android devices (as well as the Microsoft Surface notebooks) do not have pressure sensitive screens.
So, if you want to have pressure sensitivity when you draw, you need to use a stylus that senses when you press down (as opposed to the screen sensing the pressure); the stylus then sends a Bluetooth signal to the iPad.
The drawing application (in my case Adobe Sketchbook) catches this signal and makes the line you are drawing fatter. (Of course, the app must be compatible with the Wacom pressure sensing Bluetooth protocol.)
It works great, with zero lag time!