No because the noise is doubled too ;) That said the output level of balanced input is the same since the Bryston drops the negative leg. Ie 3 pins enter, two get grounded, 1 continues through the amp. I'd have to look again but its also possible Bryston sums the input, same difference.
No, no, no!
The Bryston's balanced input is differential: i.e. it "reads" or "sees" both the non-inverting and inverting input and converts it into a SE signal.
This is a Common Mode Noise rejecting input.