I find my mk7 pretty neutral at higher speeds if you use the diff to pull it round, I haven't taken it on track as it would be a waste of track time in my view, it's a sporty, practical road car.
With the considerable extra weight of the mk8, I don't think it would take too many hard laps for it to fall over as the tyres & brakes throw the towel in?
A friend has the GR Yaris in his collection of cars, it is more capable and also less practical than I expected. A Jeckyl & hide car,, really dull if you are not on it, which could well lead to trouble when you are?