You can use the client exe directly if you want. It's fully standalone. Also secu_login works just like before.
The launcher provides:
- Easy login and profile info
- Easy switching between 32-bit/64-bit and DX10/DX9
- Automatic client updates
The launcher also works as an installer when it's outside Crysis directory. It's actually installer + launcher + updater in one package.
You can also get the latest client exe manually without any installers from here: https://github.com/ccomrade/crymp-client/releases
Advanced users might prefer this, but using the launcher is the recommended way.