disabled except for life360 which allows him to communicate with us and allows us to keep track of him. We occasionally enable various apps on it for him for other things as well including games, camera, calendar, clock, etc. But he can't just install whatever app he wants and he doesn't have access to the web browser, although family link does allow you to setup chrome with a whitelist only so he could only go to pages we allow.
The only thing it lacks is fine grain control of phone and sms apps. So we disable those. The phone plan doesn't include any minutes and the texting can be disabled from Tello.
This may not be perfect for 12-14 age though. My son is 9 and we mainly use it when he goes places with friends or to school.