Can I use an NPN BJT transisor as a standard switch?
No, an NPN transistor is not the same as a "normal switch".

A mechanical switch will conduct current equally well in either direciton but a transistor will not.

A mechanical switch has almost no voltage across it when it is closed, but a transistor will have 0.2V to 0.5V across it when it is saturated.

The transistor requires that the base terminal be about 0.7V higher than the emitter terminal, which limits the voltage range over which the transistor can conduct current. A mechanical switch has no such limits.

By the way, applying 5V directly to the base of an NPN transistor may damage it. You need a resistor in series with the base to limit the base current.