I used have a LG Ultrafine 5k, now using a U2720Q, I also use a U2717D at work. All of these runs at 1440p
5K is definitely the best, and you can see the difference in terms of pixels, U2720Q come section, although it's not 4:1 pixel HiDPI scale like the 5K display, it's still HiDPI, and the quality is pretty good, U2717D, I can definitely see pixels on screen.
Update: I am not sure what you mean by Mac OS scaling doesn't work efficiently? I think MacBook Pro 15 inch default resolution hasn't been 1:2 retina since 2016, and it look pretty nice IMO