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Mercury
Firefox fork with compiler optimizations and patches from Librewolf, Waterfox, and GNU IceCat. (by Alex313031)
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SurveyJS
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.
I used both Librewolf on linux and Waterfox on windows. Liked both browsers but chose Waterfox to continue with. Will not compare the performance of these browsers as used them on different systems. At least Waterfox was faster than Firefox on windows. Currently trying Floorp and Basilisk. I would suggest to check Mercury as well: https://thorium.rocks/mercury