From the guides I was reading it seems the Noctua U14S works pretty well on the i7 9700k. Reviews say it cools the i9 9900k fine.
No possible way that cooler is "fine" for the 9900k. Maybe at idle or at non-boosted base clock speeds. No way that can handle the 9900k under all core boost conditions. I can't believe that, not when people with big air, AIO and open loop coolers have trouble keeping it in check. Plus, I have one, and while it does well with my four core i7 overclocked, I can't see any way it would still do so with double the number of cores much less with double the number of cores AND hyperthreads.
I like Deepcool's coolers. More in fact that I do Be Quiet's. After seeing the way they use creative "shuckster" specifications to make their products seem like have the lower SPL than Noctua, by limiting RPM and airflow but conveniently failing to mention that on their documentation, and especially considering Noctua is beginning to offer similarly colored products, I don't see a lot of reason for recommending their hardware. It's generally overpriced for what it is anyhow. At least in my opinion.