NFPA79 12.6.3 & 12.6.4 Control Devices

[bouws]

It is unclear to me when I need to use 18ga wire for control circuits in a control panel and when I can go down to 26ga per 12.6.4. The I/O part is a clear distinction but the control devices part is a little foggy. What is the difference between conductors for control circuits (referred to in 12.6.3) and conductors for control devices (12.6.4)? It seems to me that control circuits are the circuits that power control devices and control devices are the components used in control circuits. Does anyone know what the difference is? Thanks.