Hi Colin

Line & Arc is the best output in 2d DXF for 2d CNC (ie laser). Splines should be avoided unless you have talked with your cutting services and the tell you that they can work with splines.

If they can take a dxf file with splines, it probably gets converted to lines and arcs before it goes to the cnc machine. Even now, very few CNC machines process spline toolpaths.

You can open the dxf with lines and arcs file that you make to compare it to the original to see how the conversion went. If you don't generate the dxf with lines and arcs yourself, you always run the risk of ending up with something that does not match what you started with. Thats because the spline to arc conversion typically needs some type of tolerance value or "optimization", and this can differ between various applications.