Isn't one of the reasons you would declare an emergency in a twin with one out because (if you are not a B757, anyway), you can't really do a good go-around if the previous flight is tardy in vacating the runway.
Why doesn't someone merely open the A300-600 AFM and verify that there's a certified chapter containing performance data with one donk out of service? This issue is a no-brainer.
Actually, the problem the A306 has compared to the B-757 is that the 'Bus goes to full TOGA thrust when you hit the go levers (or whatever they're called). Not as bad as an A310 but you get a large pitch up moment even on a single engine when light.
The '75 spools the engine(s) up on the go around but then throttles back to maintain a manageable 2000 fpm climb if you are on autopilot or following the flight directors. If you pitch over to try to accelerate instead of climb before selecting another pitch mode, the autothrottle will keep adding power since it thinks you need more to get 2000 fpm.
Obviously, we are talking glass cockpit jet airliner twins here, piston twins grandfathered under some ancient rule are a different ballgame and may only take you to scene of the crash in some scenarios with an engine out from what I've read here.