The 12 core is 140W the 14 core is 165W. Think about 140/12, even on a very basic(and wrong) level you could say each core itself is using 11.6W, so 2 more cores doesn't even make it up to 165W. The reality is a lot of the power is in the i/o, memory controller, pci-e lanes, etc, which are all the same. It's probably at least 40W of power for that, so per core is probably closer to 8W, 25W more allows 2 more cores and slightly improved clocks.
The 12 core is there as the biggest yield improving catch all design, the tdp doesn't even matter, Intel breaks it massively, so the 12 core is just where all the worst dies end up so a lower base clock catches even more chips and makes them viable.
On Threadripper vs Intel, it's strange, the 18 core is going to be, well obviously more cores but not more bandwidth and due to power vastly reduced clocks. It will be interesting to see what overclockers with great watercooling can get out of it but at stock, it will gain 80% cores over the 7900x but no more bandwidth and what, ~30-40% clock speed drop.
The power difference, considering it's 140W vs 180W TDP, is crazy. AMD is providing 30-40% higher performance in so many cases while actually using less power(unless the couple reviews I've read had it completely wrong). What AMD has achieved on a tiny fraction of the budget while also going hard on GPU out of that R&D is nothing short of phenomenal. I honestly don't think there is close to another tech company that achieves so much with so little R&D spending. AMD are spending what 10% of what Intel do and splitting that heavily with GPU. AMD shouldn't be within 50% of Intel performance, absolutely trashing it on performance on HEDT is nothing short of embarrassing for Intel.