The original debate from the 80s that defined what RISC and CISC mean has already been settled and neither of those categories really apply anymore. Today all high performance CPUs are superscalar, use microcode, reorder instructions, have variable width instructions, vector instructions, etc. These are exactly the bits of complexity RISC was supposed to avoid in order to achieve higher clock speeds and therefore better performance. The microcode used in modern CPUs is very RISC like, and the instruction sets of ARM64/RISC-V and their extensions would have likely been called CISC in the 80s. All that to say the whole RISC vs CISC thing doesn't really apply anymore and neither does it explain any differences between x86 and ARM. There are differences and they do matter, but by an large it's not due to RISC vs CISC.
As for an example: if we compare the M1 and the 7840u (similar CPUs on a similar process node, one arm64 the other AMD64), the 7840u beats the M1 in performance per watt and outright performance. See https://www.cpu-monkey.com/en/compare_cpu-amd_ryzen_7_7840u-vs-apple_m1. Though the M1 has substantially better battery life than any 7840u laptop, which very clearly has nothing to do with performance per watt but rather design elements adjacent to the CPU.
In conclusion the major benefit of ARM and RISC-V really has very little to do with the ISA itself, but their more open nature allows manufacturers to build products that AMD and Intel can't or don't. CISC-V would be just as exciting.