I want create full template for my postfixadmin installation. But, what is the best way ?
Modify the files into the "templates" directory ?
I'd start with writing some add-on CSS ($CONF['theme_custom_css']) or writing an own CSS file ($CONF['theme_css']).
If this doesn't allow enough modifications - yes, then you'll need to edit the files in the templates directory.
As in your previous question, I'd recommend to use SVN trunk because the templates were changed to use smarty and are therefore completely different from the 2.3.x templates.
If your question is about adding, hiding or modifying fields, $CONF[*_struct_hook] is your friend ;-)