Jim Keller talks about his impression working with Elon - skip to 1:20:50 of this (effing amazing) interview: https://m.youtube.com/watch?v=Nb2tebYAaOA

Edit: Also Jim talks about Elon’s engineering skills at 50 minutes into this interview: https://m.youtube.com/watch?v=1TmuJSbms9c

Disclaimer: I’m not an Elon fan at all.