If you are thinking of using angle for tracks, I would suggest that angle is far from straight. Channel is a bit better and tubing is best, right off the rack. I'm talking about hot rolled here. I haven't bought enough cold rolled to know if its better, but I suspect it is. As you know, your saw will only
cut as straight and flat as the tracks it follows. The straightest thing I know of right off the rack is any shape extruded aluminum.