https://www.newyorker.com/science/maria-konnikova/hazards-automation I haven't gone deep into these studies, but I am aware that there have been claims made that large percentage but incomplete automation can have negative consequences because the human operator does not get enough practice to really be effective during the times she needs to take over. Especially in rare high leverage situations.
Anecdotally, I work in software development for a company that has a lot of services. A service that is not 100% resilient to incomplete/missing data at start up gets restarted any time its key data changes. There is no point to making something 90% resilient.
The electrons in a current never move anything close to the speed of light (https://en.wikipedia.org/wiki/Drift_velocity). It is the propagation of the changes in the electric field caused by the electrons moving that moves at the speed of light. It is more like a tube full of marbles (a stretched analogy). If you push the marble on one end the marble at the other end moves almost instantly. The marble you pushed didn't move all that distance.
Yes, the heat in conductors is caused by the electrons kinetic energy. No, it doesn't really change the propagation speed of the current since that is the electric field propagating. There is certainly power lost there.
It is not easy to transmit DC over long distances (https://en.wikipedia.org/wiki/War_of_the_currents). Edison tried hard to push the adoption of DC going so far as to publicly electrocute elephants with high voltage AC as a PR stunt to scare people. You can find videos of this online if you want. It didn't work because it just so much more efficient to transmit AC voltage and use a transformers to step it down.