Concerning sentience, I have not much to say. I think this is still far too mysterious. General intelligence however should be possible because many creatures demonstrate this. Our emulation of natural brains need not match too closely in fine detail to produce general intelligence. Much like how a plane need not match a bird too closely. The natural brains are not very similar at all to the common computer architecture you find. However, they are performing computation of a sort. Emergent properties at scale are likely to play a role IMO. We, in fact, do not know much about real neurons, but this may not matter significantly. If you wanted to faithfully reproduce a neuron, it would be a monumental task. Again, the airplane/bird analogy. Birds have billions of subsystems and the vast majority are superfluous for powered flight. I don't believe we can seriously make claims about what may or may not emerge from consciousness. We have no strong understanding of its nature. Intelligence is probably best understood as something else entirely. It is the adaptive modifications of causal paths through a network with arbitrarily chosen boundaries. We often pick the calvarium. I like to think in terms of Markov blankets. These are my humble informed opinions. Hope this helps.