Yes, the 11900k is indeed an overclocked version of the 11700k.
Yes, the 11900k is indeed an overclocked version of the 11700k.
You might consider the 10th Gen option, especially with the 10850k and 10900k models offering two additional cores. I received a 10900k which works well, though it gets quite warm during heavy multitasking like Cinebench.
It's likely the same die, only shifted a bit higher in the bins.
Fundamentally yes. The differences are minimal compared to clock speeds. For multi-core intensive jobs, it runs slower than the 10GHz model but "upgrades" the performance