PSA: ISA =/= implementation.

While it was common to suggest in the late 90s and early 2000s that there was a strong distinction between CISC and RISC styles of architecture, owing to CISC having a wide variety of purpose built instructions that aided in accomplishing specific tasks quickly, while RISC would have fewer transistors sitting around doing nothing (idle transistors do still consume some power, btw) as a consequence of bloated instruction sets, in reality, modern ISAs have a mix of CISC and RISC philosophies built in, and more important than a core being ARM or x86, is the way that core is implemented.

In reality, if you look at a variety of implementations of ARM cores, there actually isn't as big an efficiency improvement gen over gen as you would expect, as seen in the Snapdragon 865, 870, 888, and 8 gen 1 all performing relatively closely in longer tasks (though they do benchmark quite differently in benchmarks that test a series of tasks in very short bursts), and actually not being that out of line with certain x86 chips, such as something like a 5800X3D (were one to extrapolate its performance when compared to a 5800X power limited to similar wattage to the SD SoCs), or say, a Ryzen 6800U processor power limited to 5W.

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That's not to say that there isn't ARM IP out there that can be beneficial to improving performance at lower power draw, but I'd just like to highlight that a lot of the improvements you see in Apple Silicon aren't necessarily down to it being ARM, but due to it being highly custom, and due to Apple having varying degrees of control over A) the hardware, B) the drivers / OS / software stack, and C) the actual apps themselves. If you're able to optomize your CPU architecture for specific APIs, programming languages, use cases, and operating systems, there's a lot of unique levers you can pull as a whole ecosystem, as opposed to say, just a platform agnostic CPU vendor.

Another thing to note is that while Apple saw a very respectable increase when jumping from Intel to their in house M1 chips, it's not entirely a fair comparison between x86 and ARM as instruction sets, as the Intel implementation was implemented on a fairly inferior node (14 nanometer IIRC), while the M1 series was implemented on a 5nm family node, or possibly more advanced. When taking this into account, and comparing the Intel versus M1 macs, you may want to remove anywhere between 80 to 120% of the performance per watt improvements to get a rough idea of the expected impact of the node, with what's left being a combination of the various ecosystem controls Apple has available.

When compared to carefully undervolted Raptor Lake chips, or equally carefully managed Zen 4 processors, the Apple SoCs, while respectable in what they do (and being respectable as a result of many things not owing to their ARM ISA), they aren't alien tech or anything; they're simply a well designed chip.