Even if I too think 2 ram slots on a board that expensive is silly, there is actually a reason for it.
The Z590 Aorus Tachyon and the ASRock Z590 OC Formula are overclocking oriented. For memory overclocking, boards with 2 ram slots actually perform better than boards with four. That's the same reason why EVGA's Z590 dark has 2 ram slots.
The right angled power connectors are odd too, but also not uncommon on high end boards at this point. My guess is this is due to cleaner cable runs.
I wonder if there is some way to have the standard 4 memory slots with the option to only run two for speed when playing mad scientist but enable all four when you use later use the board for your working system.
In my opinion the Apex is the best looking mother board I have seen yet.
In general I don't think looks matter much and would probably buy one with green PCB if it met my price to performance marks but that is a sharp looker.
A brown Noctua cooler on that ASrock Lizard Alien green board would be amazing.
Two RAM slots is ideal for RAM overclocking. These being overclocking centric boards, it makes sense. The premium is due to the build quality. I'd bet all of these boards are 8pcb layers and above where a normal board is 4-6 layers.
On another note; The GB board is uglier than the Asrock board and that is saying something.