Thanks ! As for your question, no i didn't follow a specific guide. More like multiple ressources here and there. Here are some of them :
https://josiahalenbrown.substack.com/p/installing-nixos-with-hyprland
https://wiki.hyprland.org/Nix/
https://nixos.wiki/wiki/Flakes
https://nix-community.github.io/home-manager/
https://josiahalenbrown.substack.com/p/managing-your-nixos-configuration
If you need some inspiration, feel free to check my dotfiles
Update : i've been trying doom eternal with raytracing for quite some time now and the performance is excelent. It never drops below 144Hz with all settings maxed out at 1080p. I know that doom is really well optimised so don't take this as a general review.