Oh my, the only times I've been aware of pax sharing toilets, there was some hanky-panky going on...!!!

But it is called World Traveller Plus. So It's basically World Traveller, with a little bit more.. So it is the same toilets, (unless you're on a mid-J set-up, and I wonder if you'd be good enough to NOT share the J toilets and Club Kitchen )
And it is the same meal, but you will be seved first to ensure you get your first choice..
You're off quicker, (unless it's IAD with the funny people mover things that go to the front and back of the plane).
And you have a little more space.
I can't comment on the difference in prices, that's up to everyone to decide just how much they want something, and I don't know enough about the different fares..