That’s right about Imagine at least being begun during Let it Be. It was completed in early 1971, including finishing the lyrics. So it probably spanned God rather than being done fully before or after.
I don’t disagree at all that there is some link between the songs. They were, after all, both written by the same person around the same time. My comment was only whether there’s some consistent philosophy or view behind them that can be gleaned or John just staying whatever is on his mind and his views at that instant. Arguments could be made both ways depending on how you interpret his lyrics. In Imagine for instance he is saying “imagjne” no heaven and no hell, just sky above us. Think of how you would act if that what was the case, I don’t think he’s saying he necessarily believes it is the case. While “God” is a creed of sorts saying this is what I do and don’t believe in.
But there’s a lot of analysis that could be done on both songs. It is, as usual, an interesting question you pose Loco.