Implies low clock speed. Fetch from L1 is one of the major timing-critical circuits in modern CPUs. High clocked CPUs have small L1:s, backed by medium-sized fast L2:s, because otherwise the delay (in cycles) of fetching from L1 would get too high to reasonably hide. If you reduce clocks, you can push up L1 sizes and not have an intermediate level between L1 and the LLC. To keep performance up, this of course also implies that their design is very wide.Did they say 128KiB+192KiB L1 cache?
That's huge, Zen and Skylake are 32KiB+32KiB L1.
Regarding the non-upgradeable RAM: This has been a long time coming. In reasonably specced laptops, the energy needed to signaling to DRAM is a significant proportion of total energy budget. Going with soldered LPDDR cuts that in half. Everyone knows it would help, but so far no-one has been willing to take the leap. I suspect that now that Apple gets to be the one who sells this concept to people and makes it palatable, ultraportables will mostly switch over in just a few hardware cycles. Other laptops will follow suit later.
Going with just 8GB on the weak models and at most 16GB is a ballsy move. I think it's just too low.