Not an expert here, only been driving on AC for about 17 days 18 hrs according to CM, but I have been tweaking suspension.ini and setup.ini for a bit. Mostly just on a handful of cars: MR2/AW11, AE86, Stratos, Lotus 11. Not a good drifter here, but I put in some sessions every week.
I am assuming that you are already good at drifting. Well, I hope you are, otherwise how do you know how drift cars should drive and handle.
For a newbie, that I still call myself, I have been tweaking drift cars so that they are less "snappy" and easier for me to drive. And so my tune tend to be a bit softer, ride frequency about 2 Hz and not so drastic front negative camber, about -2. I tend to have no rear ARB or very light ones. Many drift car mod came pretty stiff and responsive and I cannot feel the car basically cannot handle them. Oddly because the drift car pack often come with pretty sticky tires, even used/scabs are sticky. These tune actually goes pretty quick on the touges that I drive, driving with less angles. And since the setup options for many of these cars are either limited or the range is limited, I had to go to setup.ini to expand them.
I supposed what I am suggesting is that drive the car and see what you want to do with it, spring rate, arb, camber, toe, ride height or damping. If the provided setup option won't do it, then dig into the setup.ini.
Just my 2 cents.