To profile performance, try this:

nix run github:crabdancing/nix-flamegraph -- -t ".#nixosConfigurations.cwilliams-laptop.config.system.build.toplevel.outPath" -o eval-flamegraph.svg

Or try evaluating just home-manager:

nix eval .#nixosConfigurations.cwilliams-laptop.config.home-manager.users.cwilliams.home.activationPackage.outPath --eval-profiler flamegraph

Then open it in the browser.

Performance stats

NIX_SHOW_STATS_PATH=stats.json nix eval .#nixosConfigurations.cwilliams-laptop.config.system.build.toplevel --option eval-cache false