The main issue with Intel's CISC/"RISC" Like Execution Engine is that it takes more transistors to implement that and the Instruction Decoders are huge relative to any ARM/RISC like ISA that has the majority of the ARM ISA Assembly Language Instructions actually translated directly to the Micro-OP format on a one to one basis, assembly language instruction to micro-op instruction. So for the x86 ISA that has most of its assembly language instructions decode into multiple micro-ops on a one to many basis there and that's a more energy intensive process there. And more transistors used to implement all that on the x86 designs use more power and leak more power as well.

It takes many times that die area to Implement a full x86 ISA Instruction Decoder compared to and ARM 64 bit only Instruction Decoder and its fewer numbers of total instructions there on say the Apple A14/Firestorm core where Apple could easily fit 8 ARM 64 bit ISA Instruction Decoders on the A14/Later Performance core designs! So the A14/Later wide decode there is 8 Instructions Decoded per cycle and all that feeds into a ridiculously large reorder buffer to extract more instruction level parallelism and get that dispatched to a very wide array of execution ports.

So and x86 core has to be much larger there and most of that is currently 6 or less Instruction Decoders wide with AMD being only 4 Instruction Decoders wide the with Zen-4/Earlier and Intel Being 6 wide with Golden Cove that's got only One complex x86 decoder and 5 "Simple" x86 decoders on that design that the tech press has never deep dived the difference there Complex/Simple in that Golden Cove Instruction Decoder design.

But the x86 cores are usually clocked around 2GHz higher than Apple's A14/Later cores in Apple's M series SOC designs and really are nowhere near as power efficient as the RISC cores there as the x86 cores are narrower and have lower IPC relative to the A14/Later Apple cores that are extra wide and high IPC in design that can be clocked well inside their Performance/Watt sweet spot range on laptops and have the best battery life metrics on the consumer market. And that's compared to the x86 cores that have to be clocked higher there and outside their Performance/Watt sweet spots where the x86 designs have to be down-clocked on battery power there whereas as the M series Apple laptops run at the same clocks on mains power or battery power.

Talk all you want about CISC and RISC but the simpler Instruction Sets of the RISC designs allow for more room for wider ranks of Instruction Decoders on the Custom ARM core designs that send that to wider execution dispatch there to ALUs, and other execution ports that are all 64 bits mostly(Neon and AVX aside) now that get the same work done only that's wider there for the custom ARM designs from Apple that have such high IPC that the processors can be clocked well inside their Performance/Watt sweet spots unlike the narrow x86 cores that have to get clocked well outside their Performance/Watt sweet spots to achieve a similar single core performance than the extra wide order superscalar A14/Later Apple designs.

And Apple's A14/Later core designs can be used in Smartphones/Tablets and Laptop/PC as well unlike the x86 designs that never really made inroads into that smartphone market. So actually is the ability of the RISC ISA processors to be made wider order superscalar there to get more done per clock cycle and well inside the Performance/Watt sweet spots there on whatever process node utilized!