Yeah distros can be confusing. For the most part it isn't too big of a deal and the main difference is the package manager. apt and dpkg for distros based on Debian (includes Ubuntu), dnf for RedHat (Fedora, CentOS, etc), and pacman for Arch. There's more but you'd run into these the most. I'll be honest, it mostly doesn't matter and it is nerdy quibbling. That said, I still think PopOS is probably the best to start out on because it has some focus around making NVIDIA drivers work. They also build their own laptops (System76) so have some extra experience there. Endeavour is good, but it is Arch based so "rolling-release", meaning you're essentially always using beta software. Mostly not a problem but can lead to some additional instability. I wouldn't expect any real issues, but should be clear.

  > "Mercury Neo with Linux 6.13.7 and Arch mirror ranking bug fix"

Yeah... that is weird to put at the top. It's a link to a new blog post. Mercury is their codename, the 6.13.7 is the Linux kernel, Arch mirror being where packages are hosted, and just prioritizing bug fixes. You can read the article if you want. Better would be looking at their about[0] or scroll down further on the front page past the mirrors. IDK why they don't put these things at the top. Definitely a mistake. Pop definitely does this better[1]

[0] https://endeavouros.com/about-us/

[1] https://system76.com/pop/