but the substituted field values may not change. they should always show the values from original user who is assigned to this article. i don't get how the subsitution has to look like.

Then your usages of the substitutions is fine. The [FIELD_NAME] usages for example will replace with the actual field value of the user and will store that value with the article. You do not need to use the {cb}{/cb} usage in CB Auto Actions. Really though you need to be able to turn off user substitution parsing so it can store the substitution that will later parse by CB Content Bot, but there's currently no way to do this.

- these joomla articles should work like pages for profiles (for comparison: fb profile and fb fan pages).

That's entirely up to you to setup. The action is just creating a Joomla article.

- every article/page has the same given layout and is generated during (or after?) registration automatically.

Acting on the after registration trigger will do this.

- user(owner) can change placeholders in profile edit.

This won't work due to the user substitution issue explained above.

- all other users should be able to see the article with the owner's values.

This will always be the case.

- create the article with substitutions. these substitutions will store the values in the article and user can not change the values by editing the substituted fields in profile edit.

Correct.

What happens when there's a trigger with on after user profile update. and the article is generated at this time?
In this case the substitutions will store the values from user's edits, every time the user updates his profile, or?

If you act on the after profile update then it'd create a new article entirely. To update an existing article you'd need to directly modify it using queries in a Query action. So that could be an option for keeping it up to date until I've added the parameter to toggle off user substitutions (unsure at this time if I can even do this while still using other substitution APIs).

Is there a way to delete the older existing article when user changes his profile?

With a direct database query using a Query action, yes.