really 
adding 200gr will give more power ?? how and why ??
With more weight the engine power is better fit on the rails.
Most of the LGB locos (and other) are more powerful because they have more weight. And they usually have only plastic gears like the Playmobil locos.
I don't know, whether 200gr or 350gr or 500gr or 1kgr are ok.
Test it, but don't use too much. Add e.g. 200gr. And then more, if 200gr were not useful.
If the wheels spin, it was too much!!
And: if the locomotive is too heavy, the plastic gears could break (the prongs break off or wear out)!!
Also you could swap the wheels/axles with metal wheels/axles to the wagons.
They roll better/more easily and so you can attach more of them.
But it's expensive (in Germany: 5,- € per metal axle).
