Let’s make an analogy with the wires. Let the wires be like a river. If it’s a small stream it can only let so much water past. While on a large river it can transport more current and even faster. Two wires made of the same substance, but of different sizes will not transfer electrons equally, because there is less metal to conduct the electricity in the smaller wire. Also, metal has shared electrons, this is why metal reflects light the way it does, and why it works so well as a conductor, the electricity literally just flows right through it!