Thank you all for your replies, I tried the most voted browsers extensively for a week (except Pale Moon), and that was interesting, I found that all forks have better privacy options than Firefox which vary from one to the other, and some add features to extend the user experience.
Being based on an older Firefox version doesn't mean they are not secure, as mentioned by the developers they are based on (Firefox ESR) which gets the latest security updates but not the latest features, which make it more stable in theory (some Linux distro use it over normal Firefox, but Windows users don't use it).
They try to be more as an alternative to chromium based browsers over Gecko engine rather than being alternatives to Firefox itself, for example Zen more like Arc, Floorp more like Vivaldi, LibreWolf more like Brave.
WaterFox is the closest to Firefox but with better options for the end user (I think I understand now why it gets the most votes) and it has the most beautiful logo (maybe more than Firefox logo too) to be honest it is what Firefox should be, the only drawback that it was owned by an ads company in the past.
Zen is promising with its feature set and ambitious and extended team of developers behind it, it gives new ways to use the web that is not traditional at all, some will like that, and some will find it hard to change what they used to, the only drawback that it is in Beta stage yet.
LibreWolf is the most private browser among others, it even disabled some security features to be more secure (which can be enabled by checkboxes so it is not that hard), the drawbacks are missing integrated password manager (not a big deal if you use dedicated one which is recommended by LibreWolf), and "Enhanced Tracking Protection" set to "Strict" with no other options (which means you have to disable it completely for broken websites), and not having built in updater (will not be a big deal if you use update software like winget).
Floorp have options more than Vivaldi itself to customize the browser the way you like (most of them are off by default but available if you need them), and it has integrated notes and workspaces (yes Vivaldi features), and set of themes (even a chrome clone theme), and it has a company behind it so it will not suffer from funding issues, the drawback is that release notes and support in Japanese.
The real problem with Firefox based browsers is that Firefox users are mostly advanced users, which mean they can implement any modifications and customizations they need using about:config.
Anyway, it is not bad to have choices.
