Paths are used to connect the general purpose interconnects , 90 degree bends...
Where as the polygons also serves the same purpose as that of the paths but these are more useful in drawing the 45 degree bends at the chip corners.
45 deg pathe are not acceptable ,u will get the offgrid errors.....by the tools like VLE,VXL..(Cadence)
for path the width is set by default to the min width of that layer . it is very easy to draw for 90 degree . but for other angles polygons are used. with paths other than 90 degrees we get 'offgrid " errors