What the OP describes is how I use Homebrew on macOS: non-standard prefix, not on the PATH. The other thing I do is use it exclusively for 'Casks' (pre-built .a

What the OP describes is how I use Homebrew on macOS: non-standard prefix, not on the PATH. The other thing I do is use it exclusively for 'Casks' (pre-built .app bundles distributed as .dmg or .pkg). If you do this, you can use any combination of Nix, pkgsrc, and MacPorts for your traditional Unix-y package needs.