> Also, how is this better than existing ion thrusters? Isn't it just a bigger ion thruster?

Besides just operating on a different principle, the theoretical exhaust velocity is about ten times higher than the highest actually flown ion thruster.

So flying the same mission with this thruster would require significantly less propellant. But you don't get to throw something out the back of the spacecraft faster for free. Kinetic energy scales as the square of velocity, so ~10x exhaust velocity is going to mean ~100x power draw.

It depends how you look at it. At one level yes it’s using fields to accelerate charged particles, but it’s using a completely different mechanism. It’s a bit like saying a turbofan and a ramjet are the same thing because they’re both jet engines.