Menu -> Preferences -> Login Window. On one of the tabs you can configure which user can log in automatically. Also, please make sure two things:
1. For the new user you created to match the one from OpenSUSE, check that this user has the same group memberships as your Linux Mint user with the different name. You want to avoid getting stuck with a user that doesn't have sudo permissions
2. Also, it may be that on OpenSUS the UIDs and GIDs for normal users start at a different base than Linux Mint. So double-check that all the files of the original OpenSUSE user are now owned by you.
As you are coming from OpenSUSE, I'm assuming you don't need me to type out any of the commands. But please share if you need more help with this