RE: Setting the default desktop settings for new user accounts
This sounds to me like a general linux question: in all distributions I tried, there is a /etc/skel directory (a skeleton), in which you can put all the files that should be installed in the home directory of newly created users (by the adduser command). This should be what you're looking for, as user based configuration files all stand in the home directory.
When you have created a default kde config that suits your needs, just copy the $HOME/.kde directory into /etc/skel.
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