@pira
The main difference between B and A (from what I could understand from this thread, is that if you don't retard one thrust lever in the Airbus (for whatever reason: Pilot error, Mechanical Problem,...)the autothrust will keep that engine in SPD mode and will accelerate the engine up to CLB thrust to maintain the SPD while in the Boeing the engine would continue to produce the same APP thrust (around 55% N1).
No SPD mode A/THR will be off, cause TR is selectet on other engine, but thrust will be produced according lever position (CLB ?).