As per your query, I understand you need to know the location in epo for the windows user credentails updated to reach EPO DB, If yes.
The core/config is the place were it will try to contact epo DB for the authentication, If your scenario is changing the password in every couple of months, then you can go for sql authentication.
>> This helps to avoid the password change from windows will cause issues for the epo login or work as normal.
>> I have attached the document with screenshots for the steps to change from windows to sql authentication.
Note: Except the epo login with default user:admin and password, the other credentails is from core/config page.
Try the steps suggested and update the status...
You are also likely storing passwords in association with each Registered Server that you may have integrated with: LDAP, MVM, NDLP, VMWare, etc.
Also, if you are using Agent installation packages with Admin credentials baked into them, you'll need to change those as well.