The iOS app should have a “Private + Tor” option for those users who want extra privacy while browsing. This feature could also be extremely helpful for those Chinese users who need to get around the Chinese firewall and who either, do not want to use a VPN or cannot afford one.
You should be able to use Orbot and put Brave into the Tor-enabled apps section
Tor support for iOS is on our roadmap. [Orbot is for Android, not iOS.]