To be honest, a real racecar is not difficult to drive in terms of handling. The games i tried so far are way to extreme in their physics for example with oversteering if you go a bit to early on throttle. A DTM car is not difficult to drive but to be quick is difficult because you need a very unique driving style. If you dont have the ability to learn or adapt your style then your to slow but a racecar in general is not difficult to drive. This is my opinion. For sure every race car has his tricks and difficulties but at the end you just have to know how to be quick, thats the most important thing. Its often faster in terms of laptime if you go a bit smother through the corner without over/understeering and fighting the car. I believe this i a bit of missunderstanding is the past years in most of the simulations.
Racecars nowadays are very good balanced and its very straightforward to know how to be quick. So what happens often is, that a lot of drivers are quick in testing for example but in race conditions they are nowhere, because of other things, mentaly or for whatever reason.
What i wanted to say is that if you want a realistic simulation its not nescessary to make cars more difficult in terms of handling. What i still miss in a proper simualtion game is that the game can simulate for example the right tyre wear ( depends on the series and tyre of course ) or simulate some pick on the tyres when you go off track or off line, or a cold set of tyres .... I missed all these things.
So comming back on the X4, I only did maybe 10 laps, but i could feel already that its closer to all DTM simulations I´ve tested so far. For sure its not 100% the same like in real and if you want i can do some proper testing with the X4 and can give you some feedback in a more detail way.