I'm using dash(sh) or bash or zsh. If possible, I would prefer to put in common place.

I want to put proper PS1 settings when I interactive with shell, so these situation should be considered


login (show PS1)
su
sudo
script (Don't show PS1)


I was put PS1 on .bashrc, but it seems not always workable.


Question: Specifying the keyboard layout for Chinese input
Answer: If it's what I think you're asking, you can set this, but it's really hard to find.  (It's not in the System Preferences app.)

On OS X in the Japanese interface, there's no "Romaji" input, but based on some screenshots I found, I'm assuming this is "英字" (eiji, i.e., halfwidth Latin characters).  All of the Japanese input methods use a system called Kotoeri (ことえり).  When a Kotoeri input method is selected, from the keyboard layout menubar menu in the top right, choose "環境設定を表示" ("Show Preferences", maybe?), which is indented a bit under a "Kotoeri" heading.  (It disappears if you have a non-Kotoeri input method selected.)  There, you can choose a base keyboard input method for Kotoeri to use.

Alternatively, there's nothing special about the (half-width) Romaji / 英字 characters: they're just Latin characters.  I don't even have this layout enabled.  When I want to type Romaji, I just use my (western) layout.  I can't tell what benefit there might be to using Kotoeri for this.

Sadly, I don't know anything about Chinese, so you're on your own there, but I suspect it has a similarly well-hidden setting.  :-)  I enabled the Chinese keyboard layouts here, and got some extra menuitems in the keyboard layout menu, but nothing that looked quite the same as the Japanese settings.