Question

yep. Kadere is correct there. You make the lightning, and where (more or less, depending on your control and strenght) you want it to hit, but from there on its only force of nature.

If the windfinders threw wind at Mat, he would be affected the same way. The power creates the wind, from there on, just force of nature.

Indeed, what lightning is is energized electrons jumping to the nearest grounded point. What the power does when it makes lightning is gives the electrons the energy they need to make the jump. Unlike fireballs, which disipate as soon as the power is no longer gathering and supplying heat, once electrons have enough energy they will jump whether or not the power is still actively trying to make them.