Create a specific project userrole for account creation, like ‘AccountAdministrator. Apply this role to the MxAdmin user.
Give this project user-role AccountAdministrator only the module-role ‘Administrator’ in the Administration module.
Then like Sairam says configure the userbase homepage Account_Overview for the MxAdmin user.
While you're at it, change the ‘MxAdmin’ username to something entirely different as best practise.
You may change another person who can able to view account overview page in Security>Administrator tab>Select that specific role.
Try to change the role-based navigation and choose “Accounts_Overview” as the target item.
You can create a Microflow and check if the logged user is MxAdmin and if the check is tru show Account_OverViewPage and if false show the defalt home page. Then Call this microflow in the DeafultHomePage in the navigation bar and remove role based home page for administrator.
If you do not want to change the MxAdmin name you can follow the above approach. But as part of good practice what Sjors Schultz says is correct.
Other wise if you are free to add an new entity to your application , you can add New entity with single String atribute and add your admin name there from UI and in the above microflow you can validate against the Logged in user. if you are changing MxAdmin name as part of good practice you can also update the Admin name in the entity you have created from UI.