Use Shapes to render splines

For a game project I'm working on a real-time in-game 3D spline editor. I'm using URP, Unity's Spline package and my own meshing around the spline.

I was mesmerized by the quality of splines in Freya's videos and was wondering if Shapes would work better for rendering splines than my CPU meshing. The rendering here is absolutely superb. I'm getting dizzy when thinking how much work it is.

My question is: What is the best approach for using Shapes to render splines?

Is it a piecewise-linear polyline, or something else? Immediate mode or not? Any tips are greatly appreciated.

• The splines need to be textured and with variable thickness within one spline.
• They also merge and split.
• There are quite a bit of general 3D object besides the splines.
• I'm OK with writing custom code shaders.
• The splines are flat (not full 3D extrusion), always facing straight up (not necessarily at the camera).