Hello All, I am new here. I might not have read everything, but I just wanted to share my view.
From the very first notion in gurbani, Ik Oankar, I can see that the guru's philosophy was very much panENtheist. The notion is saying that God is one (not there is one god, it is a bit of a different proposition to say this) and that god is beyond all that we can know (shown by the extended oankar in how we write Ik Oankar). I'm not quite sure about all this cosmotheist thing, but form what I understand, the guru talking about the cosmos are merely trying to point to everything else out there in the universe: that whatever we know of what's beyond this world, god is that and beyond that. This is to say that everything (this world) is IN god, pantheism would hold that everything IS god, and there is nothing more than this world as we know it. I am led to believe through gurbani that the guru is saying this world is a physical manifestation of god, which makes it an illusion of reality (maya), and god is beyond this maya.
edit: There is a very subtle difference between pantheism and panentheism, but it is a very important difference. Pantheist would say that god IS Maya. This is true, but maya is only the physical manifestation of god (this world) and god is beyond maya as well. this is what leads me more towards panENtheism.
I'm not sure if I answered any questions, but please let me know what you think of this explanation.
Gur Fateh,
Maneshwar Singh