I might have missed some, but apart from the car and track list, here's the info given out:
All tracks will have full dynamic time of day and weather. Changes in the time of day will affect ambient temperatures, which in turn will directly affect track surface temperatures. Tire grip will also be affected by these changes, as well as rubbering in, and weather changes.
Featuring a completely overhauled physics engine with 48 times the fidelity of its predecessors, this may be the most realistic Forza yet. That starts with the tires, which now have eight points of contact for physics calculations, rather than just one, and are updated 360 times a second.
Based on fan feedback, FM is also set to feature tire and fuel management, new “in-depth” car building, as well as multiple tire compounds. The latter isn’t specifically new to the franchise and is more of a returning feature, as it was last seen in Forza Motorsport 2 back in 2007. With various compounds, players are forced to take such variables as tire life, grip, and responsiveness into consideration.
Another area of improvement of which players will likely already be aware is the “super realistic” new suspension model. That’s set to simulate some rather complex aspects of suspension movement, including roll center, squat, dive, and dynamic force propagation.
The upcoming game also features new damage simulation and is reproduced “down to the individual scratches on the bodywork”. This includes the directionality of the damage and how the paint peels away at the exposed and raised edges, wheel abrasions, as well as dirt buildup.
Ray tracing looks to be a key feature of the new FM as well, bringing out incredible details such as those in engine bays, which have complex self-reflection. As Greenawalt highlighted earlier, ray tracing will also feature in the game “on track”, which seems to mean during gameplay and not specific cutscenes or replays.
While FH5 features ray tracing only in Forzavista mode, full-on-track ray tracing in FM should make the game feel and look more realistic than it ever has. Cars will reflect onto other cars, in their mirrors, as well as the bodywork, brake rotors, and wings, all in real-time.
According to the game’s official site, FM will run at 4K resolution and 60fps on Xbox Series X — though the console is capable of 120fps — with Series S capped at 1080p and 60fps. There’s no mention of resolution and frame rates for PC.
From:
https://forza.net/news/forza-year-in-review-2021
You’ve asked for deeper, more authentic multiplayer racing, and we set out to make that a reality in this new Forza Motorsport with a focus on growing skills and building communities. The structure of what we’ve been testing with the community is essentially a race weekend, featuring Open Practice, Qualifying, and a Featured Race with a calendar of both active and upcoming events taking place around the world.
What happens on the track with our testers is some of the best feedback we can get and that’s why we’ve had community organizers such as TORA involved. With all the changes to tire compounds, tire wear, and fuel, we’re also doubling down on endurance racing. In our last playtest, we had an Open Practice and Qualifying event up for hours. Players could practice and qualify when it is most convenient for them, then leave and return for the main event.
This new approach to endurance racing provides us with unique scenarios to experiment with. For example, we can create qualifiers during the week and host the Featured Race on the weekend, or qualify during the day and race at night.
We also want to help players unlock their fastest selves through a new corner mastery system in Open Practice. It’s designed to better focus your practice sessions on the real tricky areas of the track like double apexes – we consider those your “enemies.” We’re shaping this corner mastery system into something more social and connected that goes beyond simple per-track leaderboards and instead creates an experience where players compete and compare corner scores in real-time.
(I recommend watching the whole thing)
From:
They do say that they have updated the way that the AI works, and that has resulted in AI being as fast as the Forza RC players without the need to rubberband.
They have also said on older Forza Monthly streams that Forza Race Regulations will be fully implemented for online races and that Experimental Drag will also be a full-fledged feature for the new Forza Motorsport.
(Drag racing)
(FRR)
Also to add is the "Car building" based single-player career mode