I think 1e6 h100s could run something that’s intelligent enough to hold a meaningful conversation as in AGI assuming we figured out the appropriate algorithms and training methods.
But your description of Neurons is off. They output chemical signals, which is why painkillers can dull the signal etc. Many drugs bind to receptors on neurons which then block signals which wouldn’t work if these where electrical connections.
The do respond to electrical stimulation, and it’s often said they use electrical signals to carry information along the body of the neuron but the actual signal only moves up to ~120 m/s a long way from how fast electrical signals move. https://en.wikipedia.org/wiki/Nerve_conduction_velocity
As to simulation of a neuron, the brains got 86 billion neurons and the peripheral nervous system is doing useful work here. A full fidelity simulation of even one neuron is completely off the table simply because it’s an analog system where timing matters to an arbitrary precision, but what’s good enough is really just a question of context. Good enough to test new drugs for depression? No, though good enough to drive a car is a reasonable goal.