I do have a Dell 4k monitor (P2715Q), and it works really well and I have no complaints about its compatibility or picture quality. But I just like the Thunderbolt hub + monitor + charger solution, plus the webcam, and would've been great if these monitors came with Face ID.
The LG monitor sort of does this. But it's just ugly.
I had the Dell at my old job. Great picture quality! But 4K on 27“ is however still a compromise, since everything will show up too big when using 2x scaling. And when going for 1.5x or 2x things will get blurry. I now use 2x with smalller fonts in editors and browser zoomed out by default as a compromise.
But I’m really looking forward to have a real >200dpi desktop display for 2x scaling.
The LG monitor sort of does this. But it's just ugly.