I run MSFS on Windows 10 Virtual Machine through KVM/VFIO/QEMU on a Linux host, with a Nvidia 2080 GPU passed through. I tested MSFS on different RAM configs even before SU5, from 16 to 24 to 32 GB. Even before SU5, the amount of RAM never seemed to be the bottleneck. When I ran it on a 16GB VM, MSFS used around 12-13 GB of RAM tops before SU5, After SU5, it never exeeeds 8 GB.
My personal suggestion would be to get faster RAM with tigher timings, instead of getting more RAM. Also, I think the GPU VRAM is more critical resource for MSFS than system RAM.
If you are planning to use it for VR, spend some good money on getting a CPU with very high single core performance, like 5800x or whatever Intel’s latest is. I personally feel a processor with more than 8 cores 16 threads is an overkill for this sim, as its diminishing returns beyond 8 cores. Again, this is based on personal experience after testing with different core configs assigned to my VM 