Control point of 2D spline has two parameters for controling of properties.
One is marked as arrow - you can add a numerical value for it - it is represented as an angle.
Second is marked with diamond, it is curvature value and you can dimension it and changing values.
Start position with constrained spline. all data had dimensions.
Changing value for curvature produce following shape.
Changing angle produce following shape of spline
Changing a dimensions of control point of spline produce following shape