On this gen as a whole overclocking headroom is limited on core.
With these cpu to get all the perf you also need strong infinity fabric then run 1:1 divider high.
I don't understand, i never did expect a lot of overclocking head room, CPU's these days seem to be pushed near the limits with only 1 or 2 of the cores boosting high, if Ryzen 2000 is anything to go by you're lucky to get the maximum single core boost on all cores by overclocking, is that what you're talking about?
Yes.
How many CPUs have allowed say the +200MHz offset to frequency curve?