Hello @nemhods. Thanks for reaching out.
Running multiple security products simultaneously can create conflicts where the products repeatedly intercept each others' attempts to scan files on the system. This can create feedback loops, spiking CPU and I/O. One way to break such loops is to have the security products ignore each other. Try adding C:\Program Files\Elastic\elastic-endpoint.exe as a Defender exclusion. Then, in your Elastic Security app, add Defender (likely C:\Program Files\Windows Defender\MsMpEng.exe) as a Trusted Application.
Hopefully that helps.