sims 4 doesn't use shared gpu memory

@appelmoes1r  All the memory your graphics chip uses is shared memory.  The Radeon Vega 8 is built into the CPU and has no VRAM of its own; it has to borrow everything from main memory.  The distinction here is that your laptop is (probably, from your description) set up so that 512 MB of physical memory (RAM) is always set aside for the GPU, and it can borrow more, up to 4 GB, when it needs to for the task at hand.

It's strange that changing the in-game graphics settings wouldn't affect Sims 4's framerates, and in fact it suggests that limited VRAM isn't the issue since higher graphics options use more video memory.  Where exactly are you seeing that Sims 4 is only using 512 GB of VRAM and that other games use more?  Please post a screenshot of the value so I can take a look.  And let me know whether you're minimizing Sims 4 when checking this value.

For reference, please also run a dxdiag and attach it to a post.

https://help.ea.com/en-us/help/pc/how-to-gather-dxdiag-information/

By the way, there are different approaches that could help here, but I don't want to recommend something invasive unless there's definitely a problem that's definitely not responding to more subtle interventions.