I used to deal with a lot of wealthy as well as formerly wealthy people.
From my experience I would guess they tend to be risk takers, honest with their dealings with fellow businessmen but sometimes crooked otherwise.
I would say they were very hard workers and that is one I am certain of. They tend to live modestly but not to the extent of miserliness. Not smarter than your average person but no dummies either.
That's true of the "original" millionaires, but not for those who inherited their wealth. I had the displeasure of selling a property last year to the daughter of a billionaire, and that was a horrible process. This woman felt so entitled, and indeed she was because she was able to bully us using her lawyers. Fortunately, she overpaid by about $800K, so I don't feel so bad about it now.