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If you don't want to cut it out and redo it, the best way is to install it surface-mounted, and you must work waterproof when surface-mounted to use it with confidence. These jobs can be solved by a professional electrician.
There is also a light on the bath bomb.
The bathroom bath bomb switch has nothing to do with the size of the opening, as long as the wire is left in a position to dock, install a waterproof switch.
This depends on what brand of bath bomb you buy, some have some and some don't.
Burning wires is not necessarily high voltage, thin wires are easy to burn, high-power electrical appliances because of the large working current, the wire should be thicker, otherwise it is easy to cause a short circuit and fire.
When the ceiling is suspended, let the workers install the bath bomb, throw out the wires, and let the bath bomb workers install the switch.