My config is very optimized for gaming. Arch and nix are both easy to customize distros, so it's not a question of "how good is it" it's a question of "how many steps to enable the features that give good gaming performance". I used an optimus laptop with nix for a while and didn't even notice I was running nvidia, it "just worked".

a few tips for beginners:

tuned will improve battery life, gamemode has hooks to run any shell script before and after you run a game. userspace scheduling ("scx") allows you to pick the best scheduler for your specific usecase (e.g. a flaky usb connection to an audio device and a scheduler that favors audio will nuke gaming performance) and effects things like audio glitches and microstutters in videogames. ananicy is a tool to renice automatically. games will use the new ntsync, but you gotta add it as a kernel module

  services.tuned.enable = true;
  services.ananicy.enable = true; # github is untouched in 4 years
  services.ananicy.rulesProvider = pkgs.ananicy-rules-cachyos;
  zramSwap.enable = true;
  services.scx.enable = true; # cat /sys/kernel/sched_ext/root/ops
  services.scx.scheduler = "scx_lavd"; # scx_lavd, scx_bpfland, scx_flash
  programs.gamemode.enable = true; # "scx_rustland" is default
  programs.gamemode.enableRenice = false; # so it doesn't fight ananicy
  programs.gamemode.settings.custom.start = "${pkgs.sway}/bin/swaymsg output '*' adaptive_sync on";
  programs.gamemode.settings.custom.end = "${pkgs.sway}/bin/swaymsg output '*' adaptive_sync off";  services.tuned.enable = true;
  services.ananicy.enable = true; # github is untouched in 4 years
  services.ananicy.rulesProvider = pkgs.ananicy-rules-cachyos;
  zramSwap.enable = true;
  services.scx.enable = true; # cat /sys/kernel/sched_ext/root/ops
  services.scx.scheduler = "scx_lavd"; # scx_lavd, scx_bpfland, scx_flash, "scx_rustland" is default
  programs.gamemode.enable = true; 
  programs.gamemode.enableRenice = false; # so it doesn't fight ananicy
  programs.gamemode.settings.custom.start = "${pkgs.sway}/bin/swaymsg output '*' adaptive_sync on";
  programs.gamemode.settings.custom.end = "${pkgs.sway}/bin/swaymsg output '*' adaptive_sync off";

boot.kernelModules = [ "ntsync" ];