Do we need to turn off the custom db connection under the application and turn on the “Username-Password-Authentication” connection?
No
Or should we just leave everything(connections) as is, just remove our own Login/getUser script?
Yes, you leave everything as is, but put in the login/getUser script as per docs. That’s all you need to do.
“Disconnecting your legacy database” basically means that after you’ve changed the login/getUser script, Auth0 won’t call your physical legacy DB anymore and you’re free to shut that DB server down, close the firewall on your end, etc.