Jeff, The intended use of the product is to attach 2x4 rails to posts. You also might try to use Model #317785, depending on the nature of your project.
No I did not see any of these for 2x6.
The guy in the video is installing this bracket correctly.
I added a top rail and just notched the underside of the top rail at each end with my compound miter saw. About a half inch deep in the middle.
The code requirement for 2-1/2" screws is for a very different design that does not use these brackets. That requirement does not seem to apply.
They mount flush if installed right.
You screw the 2x4 to the bracket first and then attach to the 4x4 post.