Brave, Vivaldi, Opera, Tor Browser, Librewolf, they're all little more than reconfigurations and reskins of Chromium when you look at the entire code base. Yes, the Brave as block engine and Operas power saving modes are non-trivial, but the engine they're built on is the size of an operating system.
"Tor Browser is based on Mozilla Firefox ESR (Extended Support Release) but has been heavily modified for use with the Tor network."
Those are direct quotes from their respective web pages. Neither of them has anything to do with Chromium.
I would edit my comment above to clarify, but the limited edit time window for HN seems to have passed.