With the grid gallery view you can insert video in two areas – the header area and the grid area.
The default header area of the Template B includes Item Title 2, however you have three other Item Titles that include the image and have video option in it – these are Item Title 1, Item Title 4 and pretty custom Item Title 5 (it will work fully if you use categories). In the header area you can use either an image or the video.
The grid area allows you to insert images or image+video combination. The videos will be opened in the popup.