This is a topic that portable software is uniquely positioned to address due to the ability to have one or more of the same browser with various configurations on your system at any given time. So instead of (for example) Firefox Containers trying to separate Work, Banking, Personal, etc.
... you can have a separate browser for each of those operations, and have no risk of browser finterprinting suggesting who you are.
Some solutions from probably best to worst:
- TorBrowser with or without the Tor network - since, if you already have a trusted VPN, you might prefer that for speed or if some sites you need ban Tor connections.
- Firefox Extend Release version and just install the HTTPS Everywhere and NoScript (apart from some internal tweaks, this is mostly what makes up the standard TorBrowser)
- Standard Firefox in Private Mode (enabled by checking the box in the menu pictured below) and keeping plugins to a minimum.
To be clear, the EFF recommends the use of TorBrowser or Brave, which both are built for this operation.
Finally, I've only spent a few hours researching this so additional recommendations on this welcome.