I’ve watched this tutorial and it said to use cosine on the x-axis and sine on the y-axis. Im just wondering what would happen, or if there is any repercussions, to using the wrong “wave” on the wrong axis (like using cosine on y-axis and sine on x-axis)?

Short answer: No.

You cannot use the “wrong” function here. You can even do it with sine or cosine on *both* axes if you change the argument since:

sine(x) = cos(Math.PI/2 - x)

To put this in words: A sine is a cosine - just moved along the x-axis by 0.5*pi.

To answer the question less *literally*:

Just try it out. Nothing can go “wrong” in any sense. You might just find yourself learning something about cosine and sine functions by experimenting here. You will see that if you exchange them or add certain pultiples of PI to the argument the image in the tutorial will move in different shapes. (e.g. if you put sine on both axis with the same argument then the result should be a straight diagonal line)