im not really sure about the setups, ive had a little try and tinkered with my own setups but i cant get my head round it. i use others setups who really know about mechanics and physics, im such a noob hehe. i think it allows me to actually have more fun racing and get better hot laps than if i made my own sets, i would be so damn slow otherwise. im not fast now even with other peoples setups, much slower, but i would be worse off if i did setups too.
slowly over time i am picking things up, learning more about lines, braking, and techniques to get the best corner exiting speeds you can, which in racing has helped me to really tuck up behind others cars and make passes down the straights instead of risking corner moves that i think would be unsafe i now know how to get the best exit from said corner and make a safer move later on in the race.
learning from a hotlap, then taking it to a race track and adapting it to suit cars around you, on the track etc is definately advantageous. theres no point just following the car ahead of you, he might make mistakes and take different lines. you need to go find the line from hotlapping IMO and then take it to the races.