1) That's pretty much it.
2) If you are a professional doing work with a service bureau or printer, Postscript is still king. They do accept the others, but using Postscript generally avoids many headaches for them.
3) Sadly, font-management in OSX is still a big free-for-all. Back in the OS9 days, I was a solid ATM deluxe fan. But that's not available under OSX. Personally, I'm just using FontBook for now,
4)
Buy fonts???

There are so many resources. Adobe sells fonts. Their offerings would probably fit into your "popular collections" definition. Some of the stock photo houses now sell fonts. I especially like Veer.com's font offerings. Where you buy from depends on what you want.