Better tire/tyre model on non-grip state. Currently is not realistic and way off ...

I don't really get your point here, and I'm assuming you haven't watched the videos in the original post. Chris Harris talks numerous times about 'throttle control' and how it's the key to good drifting. In fact in the M5 video, he even says "three quarters of full throttle to hold that [drift]". Sure you need a lot of power, and at times 100% throttle, but it's all about control - constantly increasing or decreasing throttle until you hit the sweet spot, and then balancing power and steering angle.

With regard to the setup in your video, you're right. Most big engined BMWs are perfectly set up for drifting. Lots of power and torque, RWD, well balanced 50:50 weight distribution. Interestingly in that video you can hear him modulating the throttle in the audio, which shows he is adjusting the throttle to keep the car sideways/not spin off into the trees.

EDIT: Just watching the video again, and his car has a cage, handbrake extension, and more than likely an LSD or a welded diff. So this car is obviously set up for drifting.

It's a great video though! Proper hooligan!

 

Reading this make me smile a bit.
So from the beginning of those 3 pages you are conparing Chris drifting saying it's "easy" and you trying to drift...
Have you tried it in real life to say it should be easy in sim?
Lewis Hamilton saying it's easy to drive f1 today doesn't means you can do it...