How to fix a white outline around my sims 4 main menu and on loading screen

@gamerluke47  When you play in windowed mode, does the line follow the Sims 4 game window, or does it stay in the upper-right corner of your screen?  Please move the window around to test if you haven't already.

Please also disable Game Mode and Game Bar, both under Windows Settings > Gaming.

And let me know whether GeForce Experience is installed on this computer.  If you have any other software that has to do with gaming, for example MSI Afterburner or Razer Cortex, please list it too.