I agree with Owterspace
about LGMRT. Only possible problem is if you have RAM behind CPU or PCIe socket is too close.
If you are seeing Noctua coolers without AM4 mount in the box they are extremely old stock. AM4 was released September 2016 .. 2 years 8 months ago.
NH-D15s is probably a little better than U14S, but not much.
Probably because NH-U12A has 7x heatpipes and 2x Nf-A12x25 fans (best fans out right now), all in 158x135x112mm package makes it a winner in everyone's eyes .. except those who can't stand baby poo brown fan colors.