I am wondering if the FPS setting in Options>Graphics>Display>Refresh Rate would affect the load on the CPU, thereby affecting CPU core temps? An example, would CPU cores run cooler at 120 FPS vs. 240 FPS?
A game primarily loads the *G*PU, but it does also load the CPU. Yes, running at a lower FPS can lower temperatures, but you should measure before and after and see.
Note that refresh rate is not the same as FPS. But if you have vsync enabled it can cap FPS. There's a different setting for actual FPS cap.