You have a great, and well displayed collection Fabian!
Congratulations with the Bavarian General Adjudant helmet from AOK!
It looks great next to the other officer helmets in your collection. About how to display them with, or without their covers, well, this is what ever fancy's you. Everybody has their own opinion about this, so, do as you like. It's your collection.
I like the 2 French artillery adrians too by the way.