These are things Apple can fix by investing in their chip design.
The concerns (and wild speculations) come from it being pretty obvious from others that there isn't a good economical reason for Apple to make that investment. They can use their current SoC tech for the basis of every chip from a bluetooth headphone to a pro laptop. The only device that they'd support with that (IMHO massive) investment is the Mac Pro.
That said, there are technologies that do make sense that would make their SoC tech more robust and potentially more economical, such as how AMD is doing chiplets on mixed processes. I suspect eGPU support over thunderbolt 4 is coming (if not already there in the M2 Pro/Max), and a chiplet design may also help in creating alternate designs with significant PCIe lanes. Thats not to imply I think migrating their current interconnect to support chiplets and mixed hardware budget (e.g. 2/2 CPU/GPU or 1/4 CPU/GPU population in the chip depending on the hardware needs)
But, we don't get much exposure to Apple Silicon rumors - there's no third party parts suppliers leaking information, there's nobody taking money on the assembly line. So we don't _know_ much of anything.
What we can see is the M2 Max hasn't added in the modularity to match the current flexibility of the Mac Pro.
What I have observed with user replies are based on their past experience with Intel/PPC Macs and Windows PCs.
Apple is applying how the flagship smartphone makers does business onto the Mac and their other product lines.
The reason why Apple has the efficiency edge is mainly due to Apple having an edge in terms of the node they use, the PDN (power delivery network) tech, and packaging.
Their ARM cores are actually more complex than the x86 competitors; significantly wider and with larger resources for out of order and speculation. Most people assume there is some kind of "magic" that makes ARM better that x86, but that is not the case. The ISA has little impact on overall power consumption given the same microarchitectural resources.
Apple uses their larger/more complex cores to their advantage, by running them at a slower clock rate. While allowing them to do more work per clock cycle. This allows them to operate on the frequency/power sweet spot for their process. One has to note that power consumption increases significantly (way higher than linear) the higher the frequency.
Here is where the PDN technology comes into play. Apple uses the most advanced technology to distribute power to keep all the functional units feed, which requires the ability to supply a lot of instantaneous power. To do so, Apple uses a 3D stacked architecture of 2 dies; one for the logic, and another one on top (or bottom depending where you look at it) to distribute the power. In contrast, almost every one else has to use the same die to do logic and distribute power.
The irony is that a simpler/smaller ARM core would have to be clocked faster in order to compete with Intel/AMD cores. And it would end up consuming the same high power.
Apple also has a very good SoC design. Meaning that they integrate most of the system on a single die; the CPUs, the GPU, the NPU (AI accelerator), the Codec (video processing), the camera block, I/O (USB, WiFi, ethernet, PCIe/TB, etc), and the memory controller.
For some stuff like AI and video encoding, having custom silicon handling it is far far more efficient than running it on a general purpose code.
Lastly, it also comes to packaging. Apple not only integrates the SoC in a single die, but it has the memory chips on the same package. This allows them to use low power mobile DDR chips, and since they are on package it also reduces significantly all the power that having the memory transactions run through the system's PCB externally would consume.
So it's a combination of Apple using a single package where Intel/AMD laptops require multiple through their PCBs to support the same functionality. As well as Apple having access to better overall fabrication technology for that single package that AMD/Intel have for theirs.
The trend seems to be that it is becoming more efficient for mobile vendors to scale up their products into laptops, than it is for desktop vendors to scale down their products into laptops.
There is also a key difference in business models: Apple is a system's vendor. Meaning that they sell the finished product, not just the processors. So they can use several parts from the vertical process to subsidize others. In this case, Apple can afford to make very good SoCs because they don't sell those chips elsewhere, meaning that they are not as pressured to make them "cheap" in terms of area for example. Since they're going to recoup the profit from elsewhere in the product.
In contrast; AMD and Intel sell their processors to OEMs, so they only get profit from the processor not the finished system. So they have to prioritize cost, by optimizing their designs for Area first and then focus on power. This is why both AMD and Intel use smaller cores, which allows them for smaller dies. But which have to be clocked faster in order to compete in performance, unfortunately that also increases power.
This is probably their key difference; Apple can afford the larger design that is more power efficient for the same performance. Whereas AMD/Intel have to aim for the smaller design that is less power efficient for the same performance.