Five hand-drawn looks, all built from the same idea: a field of noise stretched out along one direction until it stops looking like noise and starts looking like pencil strokes.
Where the strokes land is decided by tone. Dark parts of the picture admit more ink, light parts admit less, which is exactly how you shade a drawing by hand.
The modes differ in what they do with that field. Graphic Pen is a single hard cut, the starkest of the five. Charcoal adds a second, shorter layer of strokes for roughness and keeps its ink down in the shadows. Chalk and Charcoal works on a mid-grey ground with two layers of strokes crossing at right angles, dark strokes filling the shadows and light ones the highlights. Conte Crayon fills the midtones with texture instead of a smooth gradient.
pressure means something a little different in each: how much coverage, how dark, or how sharply the tone gate cuts.