Setting the font size

Hello.

After a long time I had to leave Manjaro (mesa&AMD GPU + problems with AUR) and since I am comfortable with Arch-based distro, I compared references and finally decided on CachyOS.

I seem to be living well with you :), but I have a bit of a problem with the font size. I simply changed the settings in Plasma from 10pt to 8pt, but in SDL and GTK3 applications the font is still large. Pidgin (GTK2) is fine.

Can you please advise me how to set the font size for all apps, calmly even at system side? Thank you