I have a set of Mod 3 Binos as well as the RQE bridge setup using one of my mod 3 units and the breach. The images do not fuse, but I do not get the headaches that some speak of. You basically focus on one image or the other. I do a lot of stalk hunting, so for that, it works well. I do find that I spend a significant more amount of time focused on scanning with the Breach. I kinda work under the thought that if I don't know it's there, I can't really stalk it. But I feel if I were to use them in any type of dynamic environment, forcing my eyes to switch back and forth under pressure would not be ideal. When you have time, such as while hunting, its doable. But under pressure, it is easy to get tripped up and find yourself focusing on the wrong image when trying to aim with an IR Laser as an example. Best move there is to flip the breach up out of the way.
I'll admit that I have considered going back to running binos and then having the Breach on a lanyard, but when running on the bridge helmet mounted, I see SO much more than the guys with me that are all running Weapon mounted Thermals. I feel like I would miss a lot as well if I only scanned intermittently because I went to a lanyard hung Breach or carried it in my pocket. There have been many times where Animals have dashed out of the treeline, cut across a path, etc. that no one but me would see while stalking.