People often use two different computers:
One runs CAD, is powerful enough to run whatever CAD package smoothly (which itself depends on how complex the models are), and is in a place that is comfortable to be at for a long time while modelling (oftentimes, but not always, in a different room from the CNC machine).
The other runs the g-code sender. This machine lives close to the CNC machine, so should be resistant to dust, and ideally be cheap to replace if/when it gets damaged.
CAM software can be run on either machine. If you run it on the CAD machine, then nearly any computer that boots can be used as the g-code sender to run the CNC machine. If you run CAM on the g-code computer, then the CAM software’s requirements will dictate how powerful that computer needs to be.