I'll chime in here on the Forza physics part.
Since Forza 4 when the game got a big jump in cars from previous title and onwards, the car amount increases a lot. Forza 3 had 350 cars, Forza 4 had 450 cars. Thats 100 cars in 2 years which was the difference of the 2 titles. That equals a development time of 6 days for each car in a year of only 1 dude would make it. Of course there's more people and its a huge studio, but thats irrelevant.
The thing is, once there was an excel spread sheet posted from one of the developers on youtube which got taken down, which showed how they make the physics fast in the game. Its through a spreadsheet with an algorythm that determins the physics for the cars. They plot in the HP, weight and some other parameters which gives the car physics X, and then they give some cars a little bit of fine tuning. Thats how the dull physics get created. Every car is just a box/object of mass in Forza that only has difference in acceleration, braking, weight and rotation speed. All the cars have the same type of understeer, and same type of oversteer. Only difference is how fast or slow it happens, and at how big angle will be achieved. All the cars have the same characteristics on entry of slide, middle and exit. The difference is just the speed and how much and how long. Thats why its just some physics boxes with high acceleration, some with good handling etc. And this is why the cars are so easy and dull to drive. Sure its fun and delivers some sort of racing and adrenalin, but thats why AC and other sims on PC have cars with a more rich experience. Well anyway, the developer showed the sheet and how it all worked out, how they made physics, and how they were able to make physics for 920349042390 cars in a very small time. Thats why Forza will never be a sim, its just a game with loads of cars and an excel spreadsheet that determins how fast some cars accelerate, brake and how fast they rotate (what type of weight). Thats why its played by so many people, it becomes available to a big audience this way. The excel spreadsheet has more parameters it determines the physics for now in later time of course, with more powerful consoles, but its the same thing and thats how you create "physics" for 200 cars in a year by a medium/small team for this task.