All 5 categories get the same number of points based on order. However there are a couple things to keep in mind.
1: Any tie gets the lowest place value so if you have a group of 6 cars and 3 of them are at minimum weight allowed while the other three have a higher weight then the 3 with minimum weight would all get 1 point which is what the 6th position gets while the other 3 get 6, 5 and 4 points each.
2: If after totalling the points from all categories there is a tie then the car with the higher weight gets a 1 point bonus giving it the higher overall placement.
Also not that it means anything, but my fastest laps on both tracks have been made by a car that is well above the minimum weight beating out a couple that were right at or very close to minimum weight. Could it be faster if I made it lighter? Most likely yes but it handles very good and is extremely fast. Oh and it's not a 4wd, although it does have rediculous amounts of power.