One of the most important factors to getting a high score is the lobby strength, which is how good the players in the lobby are, not how many players total.
A x1.3 lobby can have more top tier players than a x1.5 weak lobby, this is just happenstance and is a significant factor of how much points you can likely score. In a true stacked lobby the scores that win are much lower because you won't be getting high lap score points all 3 laps and cannot just do the 1st lap skyway frontrun.
It has now become common for the top score of the week to have been done the first few hours a new World Tour cycle begins because those lobbies are x1.5 but not a stacked lobby with top tier players, it will most likely fall into the category of "top heavy".
The track selection as far as we know is random. Certain courses are much better for scoring so it is an important factor of which tracks and in what order. Farming for KO's on the first course is highly effective and if you get a course where the bumper pathing makes it difficult to farm KO's then it can be a setback to attempt farming.
Machine/track combination plays a factor as well. Stingray can start off a World Tour very strong if Stingray type courses come up early while the other machines aren't stacked with KO's yet.
The finale tracks vary in points possible by a lot. Silence & Mirror Silence are low points, White Land 2 & Fire Field, original and mirror are 2k possible but are difficult to score that high because of the competition. Silence 2 & Mirror Silence 2 are 2k possible if you are racing and 3k possible if you drive in circles until you time out.