Earlier quoted context omitted.
Exactly how is it much better? It's not the first chip with a 15-25W TDP. When compared to other chips with such a TDP, it's incrementally faster in single core and it trades blows in multicore. It does this at a process node ahead. For very light loads, it does have a slightly better power performance than existing low power PC processors, but not by that much. A Ryzen LPP core is somewhere between the big and the s…
Read the anandtech article again. 15-25w is the power consumption of the whole Mac mini measured at the wall plug. I.e it includes power supply, ssd, gpu comparable to RX560, external buses etc etc. If you want an x86 chip that beats its performance by a significant margin you have to pay more for just the chip than for the whole Mac mini.
Since both are SoCs, external buses and so are done in the chip.