I agree with the above two completely.
For the drift vs track, the parts are not what differs, as alot of time youll see the same parts , but the tuning style and setups of those parts is what differs. This was previously stated..
As for track cars being stiffer then auto-x cars most of the time that is the case, but not always. The reason alot of the auto-x cars are softer is due to budget, and streetability. Its an entry level way to get into scca racing, thus you get alot of amatures just out there having fun with their only car and sole transportation, like me. You dont want to drive a track setup on the street as it is stiff and jarring always, and its just not safe, as the streets are always full of people who dont know what they are doing. Emergency manuvering in confined and object littered areas happens alot, and you dont want to have to make one into a shoddy part of street bringing one or two tires off of the ground and loosing it.
That is another reason they are stiifer at the track is because, auto-x's are held predominantly in parking lots. They are seldom ever perfectly flat and smooth. From all I have read and heard nationals at topeka is very harsh and bumpy. Hell one of my local ones has drains that are recessed 1" into the ground, and people with street setups have become partially airborn, a few times.
As for utilizing a proper setup on the street... My setup is rather stiff for what I have, but I could add some additional stiffness

You will never utilize the suspension as much as you can on an auto-x course. The courses are just so tight and taken at the cars limit, that one will not be able to duplicate that on the street. It helps emensly in the fun factor on the street though, and I have yet to be pulled on (car in front going faster then me) or pushed (car behind me riding my ***) going into or out of an exit or on ramp
I usually am the one pulling away, or pushing the person with the exhaust that wants to rev on me prior to entering the ramps / corners. On occasion I will wait at the entrance of a on ramp going in first slowly so that the person in front of me can take their sweet time before hammering it.
One day I feel I'll get clocked doing 90 around a 30mph posted right hand sweeper, then 65 - 70 around a sharper left hand sweeper immediately after, exit ramp that is my favorite.
Also keep in mind that while the speeds are excessive, they are done at such speed only when there are no other cars on that ramp, when the conditions are optimal, and it is still under the limit of my car as my street tires or not near the max of their adhesion limits. I know they are not because I see the limits at the auto-x. I know its not the safest nor the wisest but sometimes I cant help it, and it usually gets like that the week prior to the next event (3 weeks after the last)...
But it does put a massive grin on my face, which no doubt the cop will see if this does happen
Oh and for the cone issue hehe My front bumper started to fade pre auto-x. I was going to paint it but when I smack a cone full on and hear that lovely THWACK I laugh vs cringe. Also if you are not hitting cones you are not going fast enough, or you lack the skills hopefully attained from getting to know your car through event seat time...
I dont know... I rambling... um yeah 17 days and counting (its been two months since my last event ahhhhhhhhhh)