RE: Dynamics CRM 365 menu bar
Dynamics 365 is moving to Unified Interface, and most of the Settings are moving to PowerApps. There is still lack of parity between the Unified Interface and the Legacy web client, which is why you see some of the Administration functions still available in Classic/Legacy web client.
You can access these settings by going to Advanced Settings from the Unified Interface (UUI).
Based on when your environment was created, you will be automatically directed to either UUI or classic.
You can switch between the environment by adding a parameters after the main.aspx:
forceUCI with the values of =0 or =1 to display Classic or Unified Interface
You can also go to Settings -> Administration -> System Settings, and verify the settings under the General tab:
Use the Unified Interface Only (recommended) and Show legacy Dynamics 365 - custom app to determine how your UI will start up.
Hope this helps.