Thanks for your attention on Talend. In the CSV Output component, only the option "Include Header" for the setting of the head of your file. If you check it, you will get the header and check it on the output file and if not, you cannot see the head. The head row has been run every time and you can get the different head name as long as you change your schema in studio. If the last schema is same with the last, the head will be overwritten by the newest.
Hope it will help you !
If a file with the same name exists during time of run, it is just overwriting that file without the header.