Just about every post has links to the github pages of the stuff they used

Here.

The best starting point in my experience is https://regolith-desktop.com. You install it and get a noob-friendly, pre-configured unixporn desktop out of the box.

Once you start using it, the rest of the obscure programs referenced on /r/unixporn start making sense too.

The unfortunate answer is that "it depends". Making Unix look a certain way will depend more on your workflows and preferred tools than any one particular singular grand unified guide

How? Installing the right tools and changing configuration files wich are typically (but not always) located under /home/[your user]/.config/[application]

For example neofetch config is located at ~/.config/neofetch/config But i think that's not the default config. An example config would be typically (but again not always) located at /usr/share/[application)

So what you would do is

cp -r /usr/share/neofetch ~/.config

vim ~/.config/neofetch/config

And edit the file however you want. Syntax is rarely the same between apps so prepare documentation if you do more than just change values

(Replace vim with you editor of choice)