The insulating paper in the power box can be replaced by copper paper
No, because the insulating paper used for the power supply is specially treated (including soaking, moisture proof, etc.), not ordinary paper.
You can find PVC material diaphragm (plastic film) instead, but make sure it is reliable. Please adopt!
The copperplate paper, when dry, insulation performance is possible, but without special treatment, this paper in high humidity weather will become wet and moisture insulation performance is greatly decreased or even direct conduction, so no.
