The Canon 6D Mark-2 has some awesome focusing capabilities but, unfortunately some of the important capabilities, like face detect, are connected with using live view. The face detect does a great job in honing focus on the eyes, even shooting with an 85mm lens wide open at f/1.8 It is quick and very accurate; plus you don't have to move the focus point around nor focus and recompose. I am fond of anything that makes my shooting easier and more fun.
I would have been a LOT EASIER and a LOT FASTER and MORE FUN to shoot this Mexican Dancer using face detect than it was moving the focus spot onto her face...
Unfortunately, for my eyes at least, it is virtually impossible for me to view the image on the LCD using live view in the bright sun! This is especially true when shooting with the sun in back of me. Some folks might have better eyes than I but, I just cannot see the image on the LCD well enough to use it for viewing and focusing
Enter the SWIVI Model Three viewfinder
This viewfinder is composed of two parts: a plate that attaches to the tripod screw at the bottom of the camera and the viewfinder which slides into the plate and attaches securely to the camera. This is shown with the plate attached...
The SWIVI is adjustable so that the viewfinder can be flush against the LCD, blocking out any stray light...
The SWIVI includes a diopter for focusing on the LCD and a door which can shut the viewfinder for long exposures.
The SWIVI can be tilted up to give you access to the LCD while still screening it from stray light which can be very handy when using a stylus to take advantage of the touch and shoot capability of the 6D2,
While the addition of the SWIVI viewfinder makes the camera a bit bulky, the viewfinder really doesn't add much additional weight to the camera/lens set up. Any disadvantage is made up for (IMO) by the wonderfully clear view you get of the LCD. I have not seen such a large bright viewfinder view since I was using a Hasselblad camera with a straight down "stovepipe" accessory viewer