In absolute numbers Wehrmacht peaked in 1944 if we include everyone and SS. But most of them could not really achieve anything since it is really hard to fight war without officers, weapons, supplies, communication, organization etc etc, what ever units were lacking at the moment. Often units assigned to operations were best part of German armed forces, while rest were far inferior. In battle of Bulge Allies beat back best Germany had left, other units were mostly inferior.In absolute numbers, the Wehrmacht peaked in 43.
18 million was total number of troopers who served for Germany.
Germany in WW2 was brilliant example of how to fight with ad hoc. Germans did mistakes no doubt, but it was great achievement to keep fighting as long as they did. Germany was not ready for long war, and neither were none of Germany's allies. And Germany found herself in middle of long war of attrition.
Very best of the best Germany had was often superior to what others had. But they had so very little of it that most of the time German equipment certainly not superior.