kwohld With your monitor plugged into the RTX 5070, this GPU will automatically be the one rendering anything that appears on the monitor.
Please use Display Driver Uninstaller to remove your graphics driver rather than going through the Device Manager. There's a reason DDU is the recommendation.
Please also try installing a slightly older Nvidia driver. You can get them here:
https://www.nvidia.com/en-us/geforce/drivers/
Select Game Ready Driver as the Download type, and try the version from November 4 or December 4. It's easy to update from there, IF you need to (but these drivers should be fine for a while); however, going backwards would require using DDU again.
Additionally, if your graphics card is overclocked, reset it to stock speeds. I know you mentioned this in your original post, but I'm mentiong it in case you tested at stock speeds and reverted to the original overclock.
Finally, please remove any compatibility mode you're using for Sims 3. It's not necessary and can make troubleshooting more complicated.
If none of this helps, please post a new dxdiag.