Hi Konstantin @tenzink,
I am glad to hear that you found the playground useful. Since you said you are new to neural networks, and that I see you have posted a couple of other topics on neural network architecture in this forum, I believe you must have gone through some thinking processes and did some readings. However, I have not seen any supporting reasons behind those ideas that you have asked about. It would be much more helpful for the readers of this forum if you can elaborate them more. Having said that, I think there is no need to rush, and we can wait until you are ready to.
I would also like to share with you that this Machine Learning Specialization will not be enough for you to explore neural network architecture in depth. You probably need some more advanced courses such as the Deep Learning Specialization. For example, in the DLS, there are lectures and labs that show you and let you practice how to build deeper networks, and how we address challenges in building and learning with them.
Cheers,
Raymond