To cut straight to my noob questions:
Will I only be questing/dungeoning straight up to 50?
Practically everything you do gives XP. You could level from 1-50 just farming if you want although I would recommend doing the story quest since it's the only way to get gilda stars for buying houses and stuff aside from doing the small handful daily quests.
Is PvP only open world, and can I compete in open world combat before 50?
The early zones are non-PVP for your same faction but the later zones are generally in a state of unrest or war which means you can attack other players of the same faction if you put yourself in bloodlust mode which just requires a hotkey press and is instant. A couple of times per day there are peacetimes in those zones where you can no longer attack other players. If you travel to the other continent then you are always attackable by the other faction no matter what level you are but I'm pretty sure you can't attack someone else first if you're in one of their safe zones. The open sea works like the other PVP zones and has times of unrest and peacetimes.
Can someone describe crafting and the economy for me?
There is a lot of stuff to craft but basically most stuff in the game is player made and the best stuff always is player made. There are many niches to fill, you can do farming of crops, animals or timber. From animal can get stuff like eggs, hide, fur/down, honey...all sorts of stuff that is required to make other items. You can even breed animals if you manage to get males and females. The males are very rare. You can plants trees that give fruit which you can harvest a few times per day. Or you can grow trees for lumber. There's also underwater farming and fishing. It's quite deep.
The other part of the economy is doing trade runs where you make an item at specialty crafting stations that make unique goods and then you deliver them to other parts of the continent for gold or risk taking them overseas for more gold or gilda stars. While you're carrying a pack you move very slowly and if die anyone can take your pack.
What are the "extracurriculars" outside of quests/dungeons? I keep hearing about piracy and farming, anything else? I started archer/shadow play, I'm assuming that's okay?
Aside from the stuff I mentioned you can build boats for pleasure sailing, transporting goods or naval battles, you can look for treasure in the ocean, you can decorate your house and you can even get involved in real estate since you can buy and sell houses that are already placed.
Piracy comes from attacking players in the open sea or trying to delivery goods on your continent and stealing their goods for your own profit. Going in to bloodlust mode and killing your own faction is a reportable crime as is stealing crops that someone planted outside their land. If you're reported you may face a trial and get sent jail and you get infamy points. If you get too many infamy points you become a pirate and can be attacked by anyone at any time, even your own faction. There is an island that is basically a pirates haven and you'll probably have to live there if you become one.
There is also a 3rd continent where either faction can build their own cities that are attackable but that's a whole other side to the game which I'm not that familiar yet with.
There is more stuff but that's the gist of it.