TYPO3 v8 has reached its end-of-life March 31st, 2020 and is not maintained by the community anymore. Looking for a stable version? Use the version switch on the top left.
You can order Extended Long Term Support (ELTS) here: TYPO3 ELTS.
You can enter TSconfig for both backend users and groups. The resulting TSconfig for a certain backend user is the accumulated TSconfig for all the backend groups he is a member of. Thus you can override formerly set options from the user groups by entering another configuration in the TSconfig field of the user himself.