// Auto size
new Path()
// Static size
new Path
{
    AutoSizeAxes = Axes.None,
    Size = new Vector2(100)
}
// Relative size
new Container
{
    Size = new Vector2(100),
    new Path
    {
        AutoSizeAxes = Axes.None,
        RelativeSizeAxes = Axes.Both
    }
}