How many A should be used for the switch and how many square meters should be used for the wire?

It depends on what electrical appliance the switch controls and how much power it has.

If it is a lighting lamp, the most common switch is 10A, and the power cord is 1.5 square copper core.

If the switch is an electrical appliance for controlling high power, it should be 16A, and the power cord should be 2.5 square copper core or larger. If the electric power exceeds 3500 watts, the ordinary switch is not suitable, and the air switch can be directly used to control the on-off of the electric power supply.