Is this the word for 'the rich / the wealthy'?
No, it's the word for "wealth."
No, I would say more "los ricos" for the rich/wealthy.
What about 'richness'?
I think wealth and richness are the same. Why do they give us a choice if they're not going to accept it. Dropdowns are futile.(meaningless)
What if you were just wanting to say "the wealth"? How would you know the difference?