Would not recommend under clocking. Buy a kill-a-watt measure your idle that's your general power usage. A cpu that has a low TDP and newest generation is going to be the most efficient. After that it's each item you add adds more usage at idle which is going to be most of your time. Transcoding efficiency doesn't matter much since you are likely not transcoding when you aren't watching videos. Have an appropriately sized power supply that platinum or gold certified, usually the extra cost will be justified by power bill usage over a year or 2.
For example my older gen server, a dell r720xd, sits about 120-130 watt but with 9 spinning disk drives each about 5w per hour it sits around 200w per hour. This does go higher when watching videos but is far from the average. 200w per is roughly $15-20 per month where I am located.
I hope this helps.
Shops that prey on the uninformed with unnecessary transmission flushes, coolant flushes and various oil and fuel additives are going to be grasping for work on EVs. Brakes on an EV should last longer in theory, regenerative braking doesn't use the brake system as much though the cars are heavier. I assume unnecessary brake jobs are going to increase.
Doing oil changes and other fluid myself on ICE cars I am only really going to a shop once a year for state inspection. An EV would be practically no maintenance to me. I'd say I'm out of the normal though because identifying and repairing brake, tire and suspension issues generally I can do myself.