Regarding 1, I haven't seen comparisons to the overall energy consumption of the banking sector, but a lot of people have talked about the per-transaction energy of bitcoin vs other kinds of transactions, and the ratio is pretty crazy. I don't think banking is "particularly energy-efficient", but there's not a lot of reason for it to be especially energy intensive. The information surrounding accounts/transactions/portfolios etc is all pretty concise.

https://www.statista.com/statistics/881541/bitcoin-energy-co...