So it turns out Line (Ex9.Geometry) helppatch does not make use of the actual Line (Ex9.Geometry) node, but a legacy one. Thus the framerate drop (instead with "legit" node, perfs are similar to dx11). And yes, it breaks\splits corners too.
Attached the points. It's still messy, since I have to separate them for each curve, also the coordinate system is not XYZ but XZY, and elevation (file's last element per line, AKA Y in XZY) is out of scale too, furthermore some data are missing and curves must be manually fixed, but it still gives an idea.
I haven't been able to see any AA with the constant fx.
The visual idea is: "lines" defining every curve.
With "lines" I mean a graphic element that is subject to perspective (near bigger, far smaller), but in "LookAt..." flavor, that has not broken\split corners, adjustable width: a real world example could be a round tube (using such a tube mesh would be such a mesh, since it would be around ~1500000 polys).
I also found this contribution, but it's dx9 and 2d only; anyway think about this, but 3d.
Line (Ex9|Dx11) does this, except for those ugly corners. Thus Bezier nodes could be of some help, but I be damned if I got how to use them.
points.zip (247.3 KB)