Hi,
The second IntelliSense popup looks like it’s coming from another VS extension. Most likely, it does not recognize VisualGDB, and tries to show its popup nonetheless. You can try disabling other VS extensions to see which one it is.
Another option would be to change the mechanism used by VisualGDB to display the suggestion popups (Tools->Options->Text Editor->C/C++(VisualGDB)->Advanced->Code Completion->Smart Suggestion List GUI). Some of the options there could interfere less with the other extension.