It should be but I think the 9900k could be binned by default, hence the higher turbo, so 5.3 will be hard(er) to achieve on the i7 IMO.
All products are sorted in bins at the factory. i7-9700K and i9-9900K are obviously different bins, so technically all products are "binned".
Some people mean something different with "binning", like the sub-binning some of the AiB vendors do for GPUs, where they re-test the GPUs and determine which ones are better.
In average, I believe any overclock x will be a little harder to achieve on i7-9700K vs. i9-9900K, there might be a little difference if you're trying to set a record. But sometimes you are bottlenecked by other factors leading to a similar maximum overclock. Sill, you have to remember that overclocking is becoming more and more just symbolic with such high clocks out of the box. Now you need to bump voltage and have extreme cooling just to get a few hundre MHz extra, it's not like old Sandy Bridge any more, where easily get a good overclock before even touching the voltage. If you're overclocking for the experience of overclocking, then go ahead, that's the only reason to do it at this point.
That is in one application. Cores is better than SMT but I'm sure there are applications in which it always is a help. Linux seems better at handling threads than Windows.
The Linux kernel is surely much better at scheduling, and even allows a lot of finetuning for various workloads, but that applies to specific server workloads.
SMT scales poorly with many applications at once, part of it is the OS kernel's fault, and part of it is that any synchronous task will suffer from the added latency.