I don’t think this is necessary anymore with total cookie protection being enabled by default https://blog.mozilla.org/en/products/firefox/firefox-rolls-out-total-cookie-protection-by-default-to-all-users-worldwide/

VPN can sometimes be unreliable. I’ve gotten disconnected from zoom meetings when using the zoom app and a system wide VPN. Also have lagged during online gaming. The extension could be useful if you are only looking to increase web browsing privacy, while keeping a better network connection for other programs.