>” the existing parental controls on the devices you buy and hand to your kids”
I would hope they are. Significantly better now than they were a few years back when I had cause to,investigate:
Xbox - generally good, but due to the (designed) security setup of the Xbox, my son could easily disable them (from his limited account, use browser to visit the Xbox management console, wait a few minutes and Xbox will automatically login as administrator.
Android: Gave up Set up as adult phone with password needed to install apps.
IOS: Just as problematic as Android, plus with family there was no block/limit on child spend against adult bank card…. So best set up as an adult phone with password needed to install apps.
Windows:…
Naturally, all different in the controls provided and the way they were configured. So easiest solution was computer and Xbox in the lounge, not the bedroom.