Firefox, Brave, Vivaldi.
For Vivaldi, I disabled all Google services. Go to settings > privacy > Uncheck all under Google services and Google extensions. Like Crypto Token, phishing and malware protection, DNS.
For Firefox, I modified the about:config section.
CRX extractor downloader - To download extensions from the Chrome web store and then install them manually in developer mode. It takes time at first to download all the CRX files, but once you have all the CRX files in one folder, you can easily install the extensions with drag and drop. No hassle to search in the Chrome Web Store each time. Details here.
Trace extension - To protect and spoof my browser fingerprint. This one is very powerful in terms of fingerprinting protection. Details about browser fingerprint here
Trocker - To block tracking of clicks from an email.
Privacy manager extension - To control privacy settings. Then, easily view and delete unwanted cookies.
Ublock Origin - To block ads and trackers.
I use it sometimes, not to surf the darknet, but just in case I need to change my IP. I exclude the 14-eye countries from the nodes by adding this code at the end of the torrc file.
/tor-browser_en-US/Browser/TorBrowser/Data/Tor/torrc
ExcludeNodes {au},{ca},{nz},{uk},{us},{dk},{fr},{nl},{no},{de},{be},{it},{se},{es},{il}
More details here: How to use Tor Browser Country codes on Windows, mac and Linux
I was a fan of Opera years ago, but not anymore. As I read the Opera privacy policy here, they are sending data to Google. There is no way to disable it, so I stop using it.