I don't know the answers to these questions. I'm not a professional graphic designer. I do know that Photoshop and other tools support working in different color spaces, wider than those that can be displayed on the web (which uses sRGB as a standard, covering only about a third of human color vision). Some very high-quality monitors support a very wide gamut of colors, and I would assume (but don't know) that those are used for exceptionally high-fidelity graphic design work.