SoInvaders can use Estus, but at half the normal healing rate.
Neat.
It does dictate your starting stats and equipment, but as in all Souls games you aren't locked to them. Pick a class that seems like a good fit for you at first, but know that you're free to branch out!
Cool, just wanted to make sure. I guess they are doing the class thing to give newer players more guidance starting out. Makes sense. Mercenary and Assassin look pretty cool.