PC gaming has fewer built-in parental controls than consoles. Most of the work is done via Steam's Family View and keeping Discord configured sanely.
Steam client → Steam → Settings → Family → Family View → Enable. Steam walks you through picking a PIN and choosing which parts of Steam your kid sees.
During Family View setup, tick games your kid can play. Everything else is hidden. You can add more later with the PIN.
Same setup wizard. For younger kids, block all three; they launch games and that's it. For teens, community + chat are usually fine.
Family View covers this automatically — any store action requires the PIN.
If your child is under 13, their Epic account is automatically a "Cabined Account" — chat, purchasing, and custom content are off by default until you approve.
Parental Controls → Voice Chat → Filtered, Text Chat → Friends only. Covers Fortnite and Rocket League.
If they use Discord, open: Settings → Privacy & Safety → Keep me safe, Allow DMs from server members → Off, Friend requests → Friends of friends.
Steam, Epic, and Discord all let kids stream gameplay. Off by default is fine; turn on deliberately.
esrb.org has the detailed descriptors. "E10+ with Online Interactions Not Rated by ESRB" means the game itself is fine but the chat/multiplayer is wild — decide accordingly.