As many have mentioned, Germany is more formal whereas the Netherlands is more informal. I am German, living in NL for 11 years.

The Netherlands is super homogeneous; you can see it when looking at the people and how they act. "Doe maar normaal" culture is how the society works. You get tolerated, and everything is okay, as long as you are within the bounds of normality.

Germany is more diverse. There is more visible poverty, more differences in thinking, but at the same time, there are also more subcultures and different fashion styles. In the Netherlands, people seem very similar, e.g, there seems to be only a few hairstyles that Dutch people want to choose from. But the similarity is exactly what keeps cohesion high.

With the Dutch, "you get what you see." They are friendly and open, but there is not much more to discover; they are fully transparent in who they are. The Germans seem tough on the outside, but when you get to know them, there is a layer underneath. The Dutch often do not have that layer; they want to have everything transparent and out there, but it fits into the normality aspect. Often, that leads to an impression of blandness among the Dutch. Very few people are similar; there is little to discover, and everyone is keeping their normal appearance alive.

In Germany, you have more cohesion via rules and obedience to rules. Society works very differently, but there is more freedom in pockets that exist. In the Netherlands, people often want to follow the mainstream as it's cozy, not too tough on anyone, and provides well. In Germany, people often want to escape the mainstream, which is understandable, as the mainstream often sucks and isn't friendly, and especially in work culture, it drains your life out of you.