To add to the comments of @bko and @Moors7, non-AUTOMATIC system modes can still be cloud connected, or only WiFi connected or completely untethered.
The degree of connectivity is at your own discretion and control.
In connection with SYSTEM_MODE()
you may want to read up on WiFi.connect()
, Particle.connect()
and their relatives to get a full picture to avoid misinterpretations like