compressors have only two simple characteristics, compression ratio and volume. A fridge doesn't require anything special and is essentially the same piece of metal since the 50's exept theres probaly alot less metal in modern ones.
Not true, if you can compress a real refrigerant slower you get better performance; modern control systems that can ramp up and down are significantly more efficient than older on-off styles.
It's too simplified while talking efficiency. Let's see how much A/C become efficient over decades.