I tried this yesterday with my new Galaxy S7, but right after docking the S7 with the USB connector on the HMD the Oculus Home starts automatically.
Sure it's possible to root and freeze apps...
It's also possible to set the Gear USB connector to the widest setting to fit the large phones. That made the S7 to never connect to the USB connector. But then the S7 wouldn't be fixated and it would fall as soon as you move.
Trinus VR was very unstable once getting the phone in place without being connected to the Gear VR. Trinus VR didn't clone the correct monitor either as I have 2 active monitors. It also displayed 7 FPS........
Overall, I won't be using my Gear VR with my PC as it is simply too much hassle to even set it up. And even if I
could set it up, it's way too slow to even enjoy it.
I'm a little disappointed, but it's actually something I expected. Besides there are some cool games and apps on the Oculus and Samsung app stores. I'll play those instead.