I believe the Universe to be based on rules and therefore deterministic - the difference we're talking about is really just whether we can see inside the random

I believe the Universe to be based on rules and therefore deterministic - the difference we're talking about is really just whether we can see inside the random number generator or not. A random number generator we can't peek inside doesn't make you any more free, you are still subject to making decisions based on variables outside of your control. There will always be far too much chaos to simulate large systems and make accurate/detailed long-term predictions. In terms of free will, I believe it is really some manifestation of the human mind to fool ourselves into believing we are in control. This is useful of course, because if we act as if we have agency then we make better decisions as a result and the outcome is therefore better - despite it not being possible to have happened any other way.