Shadowbringer's includes all previous expansions. If you purchase the base game and this, you would own everything. The complete edition also includes everything in one package.
Archer. Becomes Bard at level 30. You can look into Machinist and Dancer later, you won't have access to them till you progress further.
It's an MMO, so it's nothing like those other two games. It does make dozens of references to previous titles though. It's a very nostalgic for anyone who's played other Final fantasy titles. That said, it is a Final fantasy title to the main story is a big selling point. It starts off slow but know it picks up and gets significantly better as you get further in.