Warning
Create a Time Machine backup before major updates, disk operations, or security changes on macOS.
What you will achieve
Stop apps launching at login when you do not need them.
1) Remove unnecessary login items
Open System Settings → General → Login Items and remove apps you do not need at sign-in.
2) Disable background permissions
Under Allow in the Background, turn off non-essential helpers.
3) Reboot and measure startup
Confirm reduced post-login CPU load in Activity Monitor.