After starting Elements and running Organizer from the startup screen, the program (listed in task manager under "Apps" as Adobe Premier Elements 2021) will sometimes continue running Elements Auto Creations 2021 in the background. (Identified in the Task Manager "Background processes").
This hogs memory and CPU usage, causing a slower response on other programs. On my PC, the strain is sometimes identified by my PC's fan being on, presumably to provide cooling to the system.
Assuming you've got a decently-powered machine, your work shouldn't be affected by auto creations. They only run when you're not doing anything else. The Organizer also uses a lot of resources when it's first cataloging all of your media -- but there too you shouldn't see it because it only happens when your computer is idle.
That said, you can opt out of both of those features by turning off the options in the Organizer's preferences.