Most likely you want the smallest curve that’s achieves an acceptable amount of stability. Since the wave exists to prevent the wall from toppling, a pure sine

Most likely you want the smallest curve that’s achieves an acceptable amount of stability. Since the wave exists to prevent the wall from toppling, a pure sine is probably overkill. So I guess a factor then will be how tall your wall is. A very tall wall will need a deep wave, just like a wall one brick high would need no wave at all.