Miners can't choose the transaction fees, they will either process the most expensive transactions they see or just stop mining. If they stop mining, that doesn't impact the rate of transactions that can be processed.
Obviously everything I described is a simplified model where energy costs change equally for all miners. The real world is not that simple, but there is some correlation in energy costs across different regions as there is a global market for typical fuels (coal, natural gas, uranium, etc.).
It is also important to remember that transaction fees are not in proportion to transaction sizes. People doing large Bitcoin transactions could absorb much higher fees, so in all likelihood nobody would be priced out of the market (and Bitcoin would be dominated by large transactions, which is more or less the case right now).
Miners will shut their equipment down as soon as the electricity costs become greater than the rewards. When some of the miners shut their equipment down, that causes a difficulty change which makes mining profitable again for the remaining miners, and also keeps the transaction rate the same. The miners have no way to impact what transaction fees are acceptable because they have no control over the transaction rate.
The reason it impacts coin prices is that higher transaction fees make Bitcoin less desirable as a medium of exchange and reduces demand. To put it another way, let's say I am paid in Bitcoin. If transaction fees increase, I will need to demand a higher nominal salary, at least enough to cover the transaction fees incurred when I spend my salary. Likewise, any merchants that accept Bitcoin payments will raise their prices, to cover the fees they will have to pay. Yet the same work is being done and the same goods are being sold; hence, inflation, or in other words, the value of Bitcoin has decreased.