I also intend to jump from a 5900X to a 9950X, because I am interested in floating-point computations and 9950X brings the greatest increase in FP throughput si

I also intend to jump from a 5900X to a 9950X, because I am interested in floating-point computations and 9950X brings the greatest increase in FP throughput since 5 years ago, in 2019, when Ryzen 9 3950X provided double throughput in comparison with the Coffee Lake Refresh of the previous year. A 9950X contains 256 FP64 FMA units per socket, in comparison with the 128 FP64 FMA units of 3950X to 7950X. However, according to the AMD site, 9950X behaves as badly as 7950X when using 4 DIMMs. For a decent memory speed, you must use only 2 DIMMs. Nevertheless, this is less important than before. Now with 2 DIMMs you can have 96 GB, which should be sufficient for most applications.