https://vulkan.gpuinfo.org/
list of GPUs that support vulkan

• First of all credits to the original author: Doitsujin@Github
  
• https://github.com/doitsujin/dxvk <------------- What you'll need
  
• dxvk-2.5.3.tar.gz or dxvk-2.0.tar.gz

EDIT: You can try using 2.5.3 even if you are running -sfm_shadowmapres, it seems like it works on some systems.
EDIT 2: 3/10/25 : It seems like using -sfm_shadowmapres 6000 smooths out performance even more if you use shadowres
All you'll need to do is drag and drop the d3d9.dll from the x32 folder into steamapps\common\SourceFilmmaker\game\bin


extra information sourced from thencourt

Originally posted by thencourt:

Older GPUs and NVIDIA's Kepler architecture (most GTX 600/700 series) might not be supported. A GPU with Vulkan 1.3 or higher is required.
Full details on driver support: Here
Sessions that previously required up to 3GB of memory can now run using approximately 1200–2000 MB, depending on the number of unique textures.
Reduces crashes caused by memory leaks (e.g., when switching between sessions).
May not work on older GPUs.

Originally posted by thencourt:

Using RTX 3060 Ti, RTX 3070M, RTX 4070 Ti, and RTX 4080 Super, the following results were observed:
Successfully spawned about 4000 unique models in one session (based on infra tests).
Maximum memory usage with 4000 models was approximately 2600 MB.
In heavy sessions under real conditions, maximum memory usage was around 2100 MB.

images by thencourt