I tried your method to translate invitation emails logging in as admin in different languages and storing text but it seems the component is not creating tables for each language. I checked aworewards_lang_text table and only es-ES is stored there although I tried saving it in english etc.
I noticed using TinyMCE editor doesn't save the config (save and close buttons dont work), so I used JCE which in theory saves it correctly but only in main language, no matter what language the admin is in.
Regards