in 4.8 I would load up some data to build a spline in a c++ file. Essentially the source file contains the functions and some variables for use within blueprints. I then create a blueprint from the source. In the construction script I call various functions to get data, create spline, create spline points. However the script only builds a general guideline spline. It will have to be edited after to adjust for the level or make specific changes that affect gameplay.
The flow goes like this.
Code → create blueprint → load data → create spline/points → add meshes → fine-tune spline points (location, rotation, tangents).
Without the fine tuning the meshes will never look right.