I would actually look at the reviews/comparisons on how Forza benefits from the x3D since it looks like 2024 is not currently impacted by them. Personally I am planning on staying on 2020 for a while until the bugs are out of 2024 so I am building to the x3D. I also think that as more people complain there will be more that 2024 is going to have on the hard drive and may well benefit from the x3D architecture in the future, this is just my opinion.
Here is a review that compares different processors at different resolutions with Forza. Page 3 | AMD Ryzen 7 9800X3D review: obliterating the competition | Eurogamer.net
As you can see in this, Forza has them both about neck and neck, but MSFS 2020 has the 9800x3D with almost 30% more frames.