by Bob » Mon Jan 18, 2016 4:29 am
If you are exporting to a format that does not support transparency, the two cases are equivalent. If you are exporting to a format that supports transparency, they are not equivalent.
Black video is opaque, not transparent. If you place black video on video track 2, it will obscure anything on track 1 beneath it. It will always appear as black regardless of whether or not the export format supports transparency.
Titles are transparent except for where the title text or other objects contained within the title appear. If you place a title on track 2, the content on track 1 below will show through the transparent areas of the title on track 2. If there is no content below or the title is placed on track 1, the transparent area will appear black in the monitor panel. If you export to a format that does not support transparency, the transparent areas will render as opaque black. If you export to a format that supports transparency, the transparent areas will be preserved -- if you import that video into another project, you can place it on track 2 and the content on track 1 will show through.