Yes the B2W are a 2 camera in one unit, but its design make it a bit problematic.
As you can see in this picture the B2W are mounted quite a bit lower than what is optimal, in order for it to be able to see out into the cabin below the mirror.
If you locate it higher you run into this problem, and get good footage of the front of your mirror, and in that picture it is still mounted low, in that car i would have my camera all the way up on the tinted area.
So a few inches higher than that picture.
To have it in a ideal place for both the front and cabin camera it will have to be installed way up high on the windscreen, but in my car this meant my rear view camera was in the way, so for a few months i drove around testing it with no mirror in my car.
If you place it lower it get very un stealthy, and for the aim of the lenses it is also less optimal, you loose much of what go on in the rear seat at least.
The B2W also have modest bitrates on the cameras ( 16 and 8 mbit ) here the viofo A 129 duo IR are much better, and its rear camera are on a wire so you can still have the main camera ( front ) in the middle of the windscreen, but the cabin camera you can offset more or less to either side.
I much prefer the way viofo do it, better chance for a stealthy install of both the front and cabin camera.