yeah mostly it's microstates who are embedded in a far bigger country and are in customs union with it as well, so the policies that are okay for the bigger country are okay for them too.but you do have to worry about the strength/weakness of the currency which you have no way to manipulate
How do they set monetary policy?
They don't. That's partially why the whole Greece, Germany, EU stuff was/is such a mess. UKIP's Nigel Farage will be happy to tell you all about that.
It's similar to why various countries want to get away from U.S. petrol dollars. Because the U.S. has been manipulating its currency, (while hilariously pretending it's not, while being upset that China is manipulating theirs).
By the way, when enough countries get fed up and drop the U.S. dollar, Americans aren't going to enjoy that.