Through my research, the TDP represents the max amount of Watt a chip is allowed to output, per its specs. Coolers are rated for a certain TDP, which helps ensuring that X cooler will be able to keep Y chip under thermal control.

By analogy, it's often used to estimate how much power the chip will need from the PSU under load, though that isn't strictly correct because it doesn't account for Joule heating.

Here's where I'm unsure : in the case of an unlocked chip, when you overclock do you do so within the TDP, meaning that you can hit a power ceiling, because the TDP is hardcoded somehow in the chip ?
Or is the TDP only representative of the stock clockspeeds, and when you overclock you overcome that and never hit a "power" wall, only a temperature or voltage one ?

I have to assume this is the latter as it makes more sense.
But then I don't understand how CPUs so close in specs than the i7-8700 and the i7-8700k can have so wildly different TDPs : 65W vs 95W.
At stock clocks the 8700k is only clocked 100MHz higher of boost clock (and 500MHz of base clock). Surely those minute differences don't account for a 30W difference ?

Or is it only Intel's way of saying "this CPU needs better cooling anyway because we know you're going to overclock it" ?

Thanks for any answer :)