Control Panels generally have components from both the electrical and instrumentation/controls departments. Many control panels will contain a PLC with IO and some may have panel mounted HMI screens that require programming. Other control panels may contain VFD drives and motor starters that need to be sized by the electrical dept.
Either way, it is good design practice to separate the higher voltage 'power' components from the lower voltage 'control' components inside the panel. Many designs try to make use of a two sided cabinet and put the high voltage components on one side and the low voltage components on the other. This provides a safe barrier for any personnel working on the controls in the panel. It also may be a requirement based on arc flash.
If you have been tasked with putting together the design for a control panel and you don't know where to start you can follow these basic steps:
Step 1 - CHOOSING YOUR ENCLOSURE
Step 2 - DETERMINE POWER REQUIREMENTS AND HOW TO DISCONNECT POWER TO THE PANEL
Step 3 - DETERMINE PROTECTIVE DEVICES FOR POWER WIRING
Step 4 - LAYOUT INTERNAL COMPONENTS
Step 5 - ENSURE ADEQUATE HEAT DISSIPATION
Step 6 - OVERVIEW DESIGN FOR SAFETY
The UL Standard for defining what a Control Panel is 508A