can one tangle only the current blocks under header or can you only tangle the whole file?
the issue is again for dotfiles managed by org that these files are not proper org babel languages and look like this:

#+BEGIN_SRC conf :mkdirp yes :tangle ~/.config/mpv/mpv.conf
softvol-max=600
#+END_SRC

the manual (http://orgmode.org/manual/Extracting-source-code.html) only shows how to tangle the whole file

any ideas?

If you read the help for org-babel-tangle:

With one universal prefix argument, only tangle the block at point.
When two universal prefix arguments, only tangle blocks for the
tangle file of the block at point.

So if you do c-u first before org-babel-tangle, it will only tangle the code block at point.

I use this a lot so I have the following in my init file:

(defun org-babel-tangle-block()
(interactive)
(let ((current-prefix-arg '(4)))
(call-interactively 'org-babel-tangle)))

(eval-after-load "org"
'(progn
(define-key org-mode-map (kbd "C-c b") 'org-babel-tangle-block)))

So I can just do C-c b and it will just tangle the code block at point.

And I agree with you I with the manual (http://orgmode.org/manual/Extracting-source-code.html) has this information.

Hope this helps,

Joon