All condensing boiler replacements should start with a proper computer generated Manual 'J' heat load. Once a high efficiency boiler is specified to meet the total load radiation can be taken into account. Design water or "operating" temperature is determined by sizing the radiation for a particular room. The more radiation you have, the lower the operating temperature can be. Naturally this is all determined before the first pipe is turned.
The Buderus AM10 has to be set for the climate and the radiation employed. Controlling the water temperature for individual zones - especially when they are of the same type of radiation - is rarely needed.
Your installer should know how to do this, if he doesn't I would find a new service company for you annual service. High efficiency condensing boilers like the Buderus GB142 series deserve professional care.