Here is a simple solution to debug both your mangosd.exe and realmd.exe from Visual Studio simultaneously.
* Open your MaNGOS solution in Visual Studio
* Right-click either the 'mangosd' or 'realmd' project and select 'Properties'
* Under 'Debugging' set the 'Working Directory' property to $(TargetDir)
* Click Apply and repeat for the other project.
* Right-click the project you want to debug, hover your cursor over 'Debug' then select 'Start new instance' and it should start debugging
* (Optional) To enable exceptions hold Ctrl + Alt + E and make sure C++ Exceptions, Native Run-Time Checks, and Win32 Exceptions are checked. If you get an exception like 'Control + C' that's normal, you can ignore it and continue.
If either crashes, just copy/paste the error from the debugger here.