Neither Elon Musk nor John Carmack are engineers, certainly not rocket engineers. Musk is a businessman, Carmack is a programmer. Both are world class in their respective fields.

But they are also pretty good at roleplaying engineers. I suggest watching the latest Tim Dodd videos when he tours Starbase with Elon Musk and you'll see Musk engineer character. No nonsense here, no Mars colonies or hyperloops, just the practical considerations of rocket building.

As for John Carmack, my preferred example is that short discussion with Elon Musk on Twitter. https://twitter.com/ID_AA_Carmack/status/536277962803650562