based on current trends, it's going to be a parallel manifestation like Newton/Leibnitz calculus, the invention of radio, the 80's PC revolution, etc.
one could argue that the largest entities with the largest scale of compute can ship privatized AGI the soonest, but then again, frameworks like the Alberta Plan (https://www.youtube.com/watch?v=PvJ14d0r3CM ) are open-sourced, as are models like stablediffusion, and from what's been observed already, AGI may depend on the training data (which is less scalable than the compute). No, anyone doing the research can conclude that this is not a black swan.

depends on the form factor. if 0 - 10% is just an implant or headset, then you would definitely feel alive. but as more neurons get replaced, and the surgeries get more invasive, I think there would be existential crisis along the way. by the time 50-100% gets replaced, there's no guarantee of a containing that many neurons in the same skull cavity, and who knows, maybe ship of theseus immortality comes with immobility. you'll feel alive in VR, but at an existential cost.