@BackupQueen Try disabling Sims 4's Online Social Features and auto-reconnect settings, both under Options > Game Options > Other. The users this has helped have had a different performance issue than you do, but it's a simple test so worth trying anyway.
If that doesn't help, try playing in a clean boot:
https://support.microsoft.com/en-us/topic/how-to-perform-a-clean-boot-in-windows-da2f9573-6eec-00ad-2f8a-a97a1807f3dd
The one service to leave enabled is the EABackgroundService, which the EA App needs in order to run. Disable the rest as described.
When you reboot your computer, go through the Task Manager's background processes list shutting down any service that doesn't absolutely need to be running, for example anything from MSI Afterburner to RGB software might still be enabled. If you accidentally kill a critical process and it doesn't restart on its own, just reboot your computer again.
Don't open anything other than Sims 4 and the EA App while testing, not even a browser window.
If this doesn't help, repeat the process, except take your computer offline before launching Sims 4. You can sign into the EA App and then put it in offline mode.
The idea here is not to play like this going forward but to find out if some other software is causing the issues. Let me know how it goes.