I’d say Safari with extensions, as it’s the default browser and no more private than any other browser (in terms of Apple tracking).
However, on my own phone, incognito is disabled (and I have no idea how or why, since I have no content restrictions enabled), so I use Brave. I would consider Brave to be the second best browser, as its has some excellent privacy features and a brilliant ad blocker; but I’m not a fan of the crypto stuff or Brendan Eich.
I used to use SnowHaze, as recommended by The New Oil, but it’s a bit clunky.
There’s also Onion Browser if you need to use Tor.