I recommend having two worksheets (the bubble chart and the scatter plot) that are each filtered to either show nothing or everything based on the number of data points. Then put both worksheets on a dashboard in one layout container.
In the attached workbook if you change the parameter to 8,000 the view on the dashboard will switch to the bubble chart.
The trick with the filter is how WINDOW_SUM() is computed. You want all of the dimensions in your view addressed (aka checked) in the Edit Table Calculation menu. For more information about how table calculations are computed, see Transform Values with Table Calculations - Tableau
Hope this answers your question!