I have been using Excalidraw for both use cases 1 and 2 with (subjectively) great results. A few points to use it for live sketching: * Having a consistent whi

I have been using Excalidraw for both use cases 1 and 2 with (subjectively) great results. A few points to use it for live sketching: * Having a consistent whiteboard orientation. In my area of work I deal with data pipelines. Sources are always on the left, consumers - always to the right * Only one or two types shapes should be used - to me, rectangle covers pretty much anything. A blackbox system? It's a square. Some logical domain? Rectangle. A specific interface? Maybe use a diamond or a circle. Excalidraw uses numbers for shortcuts, so those are always at the fingertips. * Colors should be kept to a minimum. 3-4 is plenty. Select a shape, "s" for the line color/"g" for fill color. * At the end of the day all systems exist to help humans. A human figure(stick one, from Excalidraw most downloaded libraries) should pretty much always be on the diagram.