When using fcitx on my manjaro (xfce) computer to write chinese, I get for some wrong characters. For example, the fáng from chinese "room" gets displayed the japanese way instead the chinese way (see picture at the bottom). Also for example 新, I see it only correct when in Firefox (at least sometimes when typing).
Therefore, I switched yesterday from the Adobe Han Sans to NOTO-fonts cjk but it brought no change.
In Firefox, it produces interesting output: https://imgur.com/IegkVTd.png