Torch Browser is not open source, and it still is based on chromium. It's the worst browser combination possible.
Falkon is pretty cool! I prefer using qutebrowser if it's gonna use QtWebEngine anyway. It is slower and less featureful than the main browsers, though. If you don't mind it, I'd say go for it!
I didn't know about Dot Browser, but it looks... unfinished? It's based on Firefox, so that's cool. But it seems someone would be better off just using something like LibreWolf (or Tor if you actually want some privacy).