If you want to use zh_TW.UTF-8 on system wide you should change LANG=zh_TW.UTF-8, if not, you can put LANG=zh_TW.UTF-8 into your ~/.i18n
$ cat /home/satimis/.i18n XIM=iiimf-le-xcin
It would be: XIM=htt
You change ~/.i18n for reflecting the locale you want on the user basis, or change /etc/sysconfig/i18n to reflect on system wide. You don't have to change both.
Whether I have to change both of the abovementioned. In doing so, can Chinese Input start automatically on login KDE/GNOME desktop selecting 'Language session' as Traditional Chinese/Simplied Chinese
OR
How can I evoke Chinese Input automatically whenever login KDE/GNOME (Language - Trad Chinese or Simplied Chinese) instead of starting on terminal/terminals each time.
You don't need to specify any language selection in gdm if you have edit any of the file above. If you haven't change/modify your system that relates to xinitrc package, it will help you running different input methods in X startup based on your locale.
So in general (from easiest to hardest): 1. change language selection in gdm or 2. change system wide locale thru system-config-language (only support on the languages you have ticked in anaconda) or 3. edit /etc/sysconfig/i18n directly to reflect for system wide locale or 4. edit ~/.i18n to reflect only on specific user's locale
Leon