The place to look for the answer to your first question is Ethereum - it already gave up mining when it moved from POW to POS, and the network of former miners is now occupied by ChatGPT. The Point of the story is that the amount of solar infrastructure dedicated to BTC, and vacated by then, instead of just accommodating something like ChatGPT, it might be enough for us to move all remaining non solar powered humanity over to it.
We are already almost 50% covered by solar in some countries, with most of it being domestic and community owned. The cost of all infrastructure created like this is recouped very quickly during the life of crypto miners, assuming they are successful, and get to mint some coins. In practice, the competition of mining each coin is spread across the whole population of miners. A miner in a small farm has the same chance as a miner in a large farm, of winning, given both have similar hardware of computation - check out "ant-miner" for example. But the larger farms will statistically win more of the time because they have more miners. But you are right a lot of folk lose a lot of money by choosing the wrong equipment or power solution, its something experienced miners would keep to themselves (Not me, I am a systems Engineer, not a mining specailist, I would be just as likely to lose as anyone if I were to try it!).
Anyhow BTC will be POS by default after the last coin is minted,
My point in the story is that it might be used to allocate power capacity, after the last coin is minted, because each one represents an amount of solar infrastructure created, because a "proportion" of the infrastructure created the coin.
If it was used like this, then coins changing hands would be a relatively rare event. The population of coins would become the mechanism of allocating power capacity to communities and causes. If the energy from the whole vacated solar infrastructure was dumped into hydrogen, then a holder might be guaranteed a capacity of hydrogen fuel, which would be useful for aerospace, so holding coins would be attractive to aerospace, for example.
We are talking about only a very small part of what is a global solution, one that we appear to be being forced to, by nature. Nature is progressively removing all possibilities of profit, at the same time as devaluing all money issued as debt, so we will have to start issuig stimulus sometime, this looks like the future function of banks, which will become more or less automated suppliers of energy as money - again ChatGPT appears instrumental in all of this.
Sorry long reply but we can only scratch the surface in exchanges like this.
Here is some analysis with more numbers:
