A. Aperture priority means that you can adjust and control the aperture. The aperture in other words is the f-stop. In aperture priority, the camera will choose the shutter speed, while she will manually be able to choose the f-stop.
I'm an amateur at digital art, so my suggestion may not be as useful to you. I suggest using the RCA Cambio, It's 32GB and comes with Paint 3D. It's also a laptop/tablet hybrid, so it's good for other things too. I got it at the affordable price of $120 at Staples