Your thought experiment cannot be completed without making further assumptions. If I were to assume, for instance, that the increased gravity of larger systems caused limitations on the design variations that worked for mobility, I would think there would be less diversity.
You ask some interesting questions, but they are mostly unanswerable either because of the way you have framed them, or because the answers are not agreed by cosmologists.
Another for instance: if you start asking about quantum mechanics, you better know higher [WAY higher] math if you really want to get an understanding of it. The more advanced constructs in physics and astronomy do not lend themselves to easy conceptualization using the English language - the language of math is required for complete accuracy and understanding.
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