I think they are matched, but haven't really tested. The Kadett GSi is the rotten apple in the pack, in my opinion. It's borderline undrivable because of a bad rear suspension. I have tinkered with a more decent one, but I'm no engineer, so it's all a load of guesswork. But I have managed to make a new suspension.ini for it that feels pretty good.
Yes! This, among other things, are details that kind of holds Tommy's mods back. Which is a shame, because the models themselves are pretty good. And a shame that he doesn't take the time to lift his cars from decent to excellent. Not really a fan of having to tinker with paymods to make them work, but I've always made an exception for Tommy. Because he makes the cars I love, that nobody else makes.