Firefox it is (Or its forks. Need Suggestions.)

• Betterfox

  66 3,626 8.0 JavaScript

  Firefox user.js for speed, privacy, and security. Your favorite browser, but better.

You have also some tweaks done for it with either Betterfox (actually like this one), which gives performance boost + privacy without site breakage or Arkenfox if you want more focus on privacy at the risk of some site breakage. There are some others but both of these are good ones.

• user.js

  683 9,201 6.8 JavaScript

  Firefox privacy, security and anti-tracking: a comprehensive user.js template for configuration and hardening

  

You have also some tweaks done for it with either Betterfox (actually like this one), which gives performance boost + privacy without site breakage or Arkenfox if you want more focus on privacy at the risk of some site breakage. There are some others but both of these are good ones.

• SurveyJS

  surveyjs.io featured

  Open-Source JSON Form Builder to Create Dynamic Forms Right in Your App. With SurveyJS form UI libraries, you can build and style forms in a fully-integrated drag & drop form builder, render them in your JS app, and store form submission data in any backend, inc. PHP, ASP.NET Core, and Node.js.

  

• Floorp

  33 4,395 9.9

  The most of source code of version 10 or later of Floorp Browser, the most Advanced and Fastest Firefox derivative 🦊

  

I've been trying Floorp for some days now and I'm finding this project interesting.

• firefox-scripts

  131 916 1.6 JavaScript

  userChromeJS / autoconfig.js and extensions

do what exactly? inject code? there are many slightly different approaches, the most reliable seems to be https://github.com/xiaoxiaoflood/firefox-scripts and using an approach like that forks can add extra configs to the UI making users' lives easier

Suggest a related project