Here's how to fix the default too wide and too "round" fonts rendered in EMACS under KDE (and maybe other DE, too).
Write this into the
Xft.antialias: 1 Xft.hinting: 1 Xft.hintstyle: hintfull Xft.rgba: rgb
After that, run the following:
$ xrdb -merge ~/.Xdefaults
And after that EMACS will really get the same-looking fonts as the other system around it. Thank you Atragor for your answer at archlinux.org