Not meaning to confuse anyone anymore than they already are.

A switch is a switch, which side of the device it is attached to does not determine the amount of the load (amperage). The load (current draw) on the switch is the same regardless the side of the device it is attached to.

In house type wiring switches are attached before the devise as this arrangement will allow the switch to operate as a disconnect of the main power to the device, which is safer for the consumer. But remember older homes (pre- 50’s) did not have earth ground and the wiring was not polarized as it is today, thus switches in these older homes can be on either side of the devise, which presented a shock hazard that was later corrected by building codes.

Car voltage is much lower and normally does not present a shock hazard, consequently switches are often on either side of the device they are intended to control with no determent. When the switch is in the off position there is no load on the device regardless the side of the devise the switch is on, a circuit must be completed to establish a load.

This is not to say a switched devise can not make electrical noise in the off position, it can in the case of the DC fans being spun by other means (generator effect), regardless the side of the devise the switch is attached to, as noise can travel through ground as well as power. However, this type of noise normally has no ill effect on most analog circuits used in our older cars other than a little whining noise in our music. Digital devices are different and they require other means of protection, which in most cases is built in by the manufacturer.