Ancient peoples had no problem calling natural things gods. The way human mind works is that it's easy to see natural events as having "character" in a way animals and humans do. The workings of the sun, giving life to plants and by extension to animals and humans while punishing them with heat at times when was practical. Supernatural is something that comes from Christian theology.
I'm not holding any philosophical ideas at this point what it could be. The reason I don't think that it's supernatural is that I don't believe in "supernatural" things, but I'm open to proof on that.
If I would try to prove it to you, it would be circular logic. Whether God is "caused by us" or the experience caused by God I hold no preference.
The God experience is a mystical one and not easy to explain. What we can get out of it is what God is not, as much of it is against traditional, cultural ideas... It's clearly not something that has desires for people to follow rigid guidelines set in stone. There are no words coming out of it, if there are, they come from whoever had the experience. There are no goals set with the experience. There is something of a purification of ideals and emotions that happens there. If we could reproduce the experience by artificial means, it would be of great value to us as mankind.
As to limitations of God I don't know except that it exists anywhere there exist humans or perhaps similar minds, but it's clear that it's up to us to experience, we don't know if God is trying to cause the experience or if it's us by fortune or skillful effort being able to reach that Gnosis.
There is a variety of religious experiences. Not all of them hold claims such as information about morality or the world. I call the religious experiences people commonly have "spiritual experiences". I don't see anything "special" about them though they are in reach of everyone and beneficial to us as long as we don't use them as excuses for something bad. As I can produce them or their equivalents pretty much by going out into the forest, by meditating, by mathematics, by music...
I can read it just fine.