1.I usually use a fine sharpie to draw on plastic but it will smear and wear off. I cut on the sharpie line and then wipe it with a tissue to get any ink off.
2.On fusible applique you cut on the line but you have to add a little extra on the edges that go under other shapes.
3.You do need to reverse some shapes if you are using a fusible but do a little sample shape to figure it out.
Draw a master sheet on paper of your completed block. This can go under a light background so you can place you appliques in the right spots before fusing.