break in a case with return.. and for default
You don't need either break, but there's no harm in having them. In my opinion, keeping your code structured is worth having a couple of extraneous statements.
I agree with having a break in a final default case, and don't agree with breaks after returns. (A colleague does those and it hurts my eyes.)
I also indent switches so as to reduce proliferation of indent levels. :) i.e.:
switch(option) {case 1: a = 1; b = 7; break;case 2: a = 2; b = 4; return -1;default: a = -1; break;}(I also think that, since the return statement is not a function, it isn't appropriate to enforce a superfluous style that makes it look like one.)
The break after your default case is just a matter of personal preference.
Putting a break after return almost seems contradictory to me. I'd remove the break, just to make the return statement really stand out.