I've decided to answer my own question: does Noctua NH-D15 fit Z490 Dark with, in my case, G.SKILL TridentZ RGB Series 32GB (2 x 16GB) F4-3600C16D-32GTZR (44mm/1.73" high), and without obstructing first PCI-e x16 lanes slot for a GPU. (because EVGA ****ed up and made second x8 lanes only)
I picked up NH-D15 and DeepCool Assassin III, both are top air coolers and performance wise are roughly the same. According to majority of the tests Assassin III is louder then NH-D15 by about 3db, which is significant because decibels are geometric progression scale, but total is still quiet enough, at least that what I hope for. lol. Noctua is marginally better made and marginally better quality, it is hard to explain, but it just feel better. On the other hand, NH-D15 is wider and it's radiator sits lower over the slots.
This was just a dry run, I did not removed CPU cover or screwed all parts tightly, so when installed both would sit @2mm lower.
NH-D15 will fit EVGA z490 Dark only with fans blowing upwards, with outside fan on top, and even in this configuration I would have to move outside fan to have clearance for my memory. It is impossible to have outside fan on the bottom because it will obstruct PCI-e 1 slot. It is also impossible to fit NH-D15 in any other orientations, because pipes spaced to wide and hit memory and cover.
Assassin III is narrower then NH-D15 and has more clearance on the bottom over the memory, it is also only will fit in fans blowing upwards orientation, but it clears memory just fine, easy to fit outside fan, it may even fit fan without obstructing PCI-e 1 slot, but air flow will definitely obstructed with fan on the bottom. I did not though about taking photos until after I started to fit Assassin III, just notice that Noctua is wider, lower and does not fit as well as DeepCool.