Language Files / Multiple Instances

Hi All

PRE-QUESTION -------
If there is anyone able to give a little clarification that would be great:

LANGUAGE FILES

There seems to be quite a few of them:

With the Framework comes two sets:

- tpl_t3_bs3_blank/language

- plg_system_t3/language

and we end up with

- my_template/language as well...

I read that I needed to change the template/language files for ThemeMagic when creating new parameters, but it seems we need to edit the " my_template/language " files for the existing ones (well, for changing 'Typo' in ThemeMagic I had to...


ACTUAL QUESTION --------
Is there a rule of them or guide or advice or tips to using the language files with T3 Framework and Joomla?

Most appreciated

Jon