Right. Normally, I dont do social history, but this would be a rather great change, so I find it intersting:
Assume for whatever reason there is no 30 Years War. Not a period of perfect peace, either, but the usual amounts of wars, ended by political balance of the two confessions in Germany as IOTL. Or whatever - as long as there is no 30 Years War. That in itself would have intersting politcial cosnequences (and would require an intersting political situation to bring about), but my point is something else:
IOTL, a third of the German population was killed in the war. In many territories even 2/3, and in others of course less, but overall roughly a third. Germany really only caught up in population in the explosion of population numbers in the 19th century. So, without the war, what happens to population development? What happens to the excess numbers of Germans?
Is Germany now constantly on the brink of overpopulation and hence due to plagues and famines there wont much change after aforementioned 19th century, resulting in cerca the same population numbers as IOTL? Or do Germans go out settling - but where? Not the far away colonies of other powers, and Eastern Central Europe is by that time sufficiently settled that unlike in the middle ages Germans cant settle there, either. More Russia Germans, maybe, but apart from that... or could Germany actually have and maintain so much more people?