This [1] has good examples. 24" 4K is on the smaller side and so less noticeable than on larger displays like 27" or 32".

[1] https://bjango.com/articles/macexternaldisplays2/

I have a Macbook pro and a Linux machine attached to my dual 4k monitors.

Fonts on Linux (KDE Plasma on Wayland) look noticeably sharper than the Mac. I don't use subpixel rendering either. I hate that I have to use the Mac for work.