Any guidance on regular web app crdentials correct usage to access Management API?

You’re welcome @h825 !

I believe you ask why in a backend service (like a regular web app) you still need to use the Management Api Client credentials and a linked to it M2M flow.

Any time you want to:

you use the M2M apps granted relevant for these tasks permissions.

In contrast, if your backend service integrate with Auth0 to perform user’s authentication and authorization, you use flows reserved to Regular Web Apps.