Love those ITX builds.
What is the purpose of this build?
If it is for gaming, you have not specified a graphics card.
My thoughts:
1. i9-9900K is a very good processor for multithreaded apps.
But, for gaming, you would perform equally well with a 8 core i7-9700K.
2. Your case is a good one. It supports two front 140mm intakes, none of which is provided. I would add two 140mm fans to the list instead of the two 120mm units you listed. Noctua 140mm fans would be a preference.
3. Noctua NH-D15 is about the top air cooler.
But, a better option is the NH-D15s which is a high compatibility version.
It is offset to clear graphics cards and it will also clear tall ram.
Noctua will have a motherboard compatibility chart to check somewhere.
If you can't find it, you can ask noctua for a check.
I doubt you will have a problem.
4. There is no negative to excessive ram. But unless you were heavily multitasking, 16gb is sufficient.
3000 speed is fine.
5. What a strange combination of drives.
Keep it simple with a single 2tb m.2 drive. 860 evo is the sata version and 970 evo is the faster pcie version.
Have you considered backup storage?
Make that an external enclosure with a suitable capacity wd or hitachi drive
6. PSU is good quality. 750w psu should be sufficient.
But, that particular psu is quite long for a small case.
A Seasonic focus 850w gold unit will cost less and be only 140mm long.