>> not so smart that you’re just lost when talking to them
That, BTW, is a sure sign that someone is trying to appear smarter than they really are. Having worked at 2 research labs over the course of my career I know more than my fair share of genius-level people. Without fail, they are humble about it, and can explain complex concepts in a way the rest of us can understand. This is something that just blows my mind pretty consistently actually, and IMO it is a sign of true, deep understanding of a complex subject. The person didn't just memorize formulas (although many of them excel at that as well), they understand why things are the way they are, the real meaning behind it all.
It could be that this is selection bias though, and I only got to know geniuses who aren't also assholes.