An ARM CPU only emulating x86 isn't going to be more efficient than straight x86. ARM is barely more efficient as it is at those performance levels.
The real reason Apple is ahead is because they're paying for more expensive more advanced nodes for their CPUs. I you compare CPUs on similar node sizes, you'll see that AMD and Intel are basically caught up architecturally in perf/W metrics.
There is no theoretical reason that is the case. These systems would be transpiling, not interpreting.
This is definitely not true. M3 is 2x - 3x more efficient than Lunar Lake on the same N3B node.