well typically how particles are done is that each particle even though it appears circular is really a textured quad (4 vertices) that is alpha blended so you only see the necessary parts. now if you used rectangles, your still using a quad. lines are drawn using different methods. Also, if the engine is using point sprites for particles, then it may be single vertices, but still in that effect he's using tons and tons of them. the key is to keep the particle count low while keeping the effect nice. the demo I have demonstrates this effect. using lines/rectangular quads along segments of the spline curve should work fine.