I can't reproduce any of those issues. When drawing the indicator snaps to a pixel, so it's perfectly clear where it's going. When I draw a line, it's pixel-perfect when moving the control points, likewise after it finalises. And when I copy a section of the image and paste it back in, it's pixel-perfect as I move and when I finalise. There doesn't seem to be a true resize; all I seem to be able to do is change the size of the canvas, which doesn't add any kind of aliasing.

But I've only used the program for less than 5 minutes, so maybe it's configured differently?