CAM should start in offline mode.
Cam should automatically start in offline mode, do the fan/AIO/LED controls, etc. Only then should it try to login. If you MUST, have it say it'll work with reduced functionality.
Controlling Fans, AIO pumps and LEDs should *never* require internet access. It should just work.
And yes, there's guest mode. Except many of us have had CAM stuck at the "Authenticating" screen, not allowing us to select it!