To edit the user creation defaults you can use the "Edit defaults" dialog, which is accessible via the menu Settings->Preferences. There you may change the defaults that are used when creating a new user: Shell and Home Directory (or home directories volume). You can choose whether to make a home directory on "create" or not, to copy a skeleton to the home directory or not. You can also enable "User Private Group" mechanism, which creates a new personal group with the creation of a new user, and removes the personal group when the user is removed.