It's not the efficiency, but a different architecture. The main issue is that, all software made on windows wouldn't be compatible if you change the CPU architecture.

Yeah, all CPUs use the X86 architecture. Or more modern versions that are backward compatible.

Apple's M1 and newer CPUs are not using X86, instead they use the same architecture as our smartphones. Which is more energy efficient, but costs more to produce if you want the same computing power.