If you don't want Microsoft Edge to start when you sign in to Windows, you can change this in Windows Settings.
1. Go to Start > Settings .
2. Select Accounts > Sign-in options.
3. Turn off Automatically save my restartable apps when I sign out and restart them when I sign in.
In task manager, have you disabled Edge under the Startup tab?
Alternatively, Right click on your desktop computer icon, select Manage, then left click on Services and Applications, then on Services in the middle section. Then scroll down to Microsoft Edge Elevation Service and also to Microsoft Edge Update service (there might be more than one listing) to see how their Properties are set.
Also, while in Services, scan to see if there are other Edge services listed, IF so, check out their properties also