1. Please find details in attached file "Capture.png" (Uncheck the makred check box.)
2. if you set
web_browser_homepage -> about:blank
enable_3dmodelspace_browser_tab -> no
then you end up having two browsers. Result is in "Capture2.png"
3. Another option: I did not find way to reduce the number of browsers but by updating few html files we can set all browsers to about:blank.
I hope all this information helps you!