In case someone should wanna know. Open krunner, pin it (upper right pin), press Alt-F3, More actions, configure special window setting, add property, position,size...whatever, force.
Fonts too can be adjusted in ~/.config/krunnerrc. For example:
[General]
font=Noto Sans,12,-1,5,50,0,0,0,0,0
The arguments are as follows: https://doc.qt.io/qt-5/qfont.html#toString

https://imgur.com/a/UWMCx2D