Drawing a frame from scratch
Where you would normally add a picture, press Draw a frame instead. This is the tool for a frame that starts empty. To mark up a photograph you already have, see Annotating a frame.
The line
Three weights, Fine, Medium and Broad, and a Rubber that paints in the paper's own colour.
Ink strength is separate from the weight: Black, 75%, 50% and 25%. A broad line at 25% and a fine line at black are different marks, and between them they cover most of what a thumbnail needs.
Drawing with a stylus
An Apple Pencil gives you a steadier line than a finger or a mouse, and you can rest your hand on the screen while you use it: once a pen has been seen, touch stops drawing, so a palm on the glass does nothing.
The line itself is an even weight from end to end. It does not thin and thicken with how hard you press, on any input. If you want a lighter mark, choose a lighter ink or a finer weight.
The drawing area is a fixed frame at the board's aspect ratio. There is nothing to pan or zoom: what you see is the whole frame.
Coming back to a drawing
A drawn frame is not flattened away. Open the shot and press Edit drawing… to reopen it in the pencil tool with every stroke still separate, so you can rub out one line from last week without redrawing the frame.
That is the difference between the two tools worth remembering: Annotate flattens marks onto a copy of a photograph, and Draw keeps the drawing editable for as long as the board exists.