I’ve tried Trinus Gyre with ArmA 3. My phone is Nexus 4, Lollipop, unrooted.
The phone cannot connect to trinus gyre via USB tethering. The server cannot detect it. So I switched to wifi, and connection is possible.
After resizing the resolution for ArmA 3 to 800×600, the game is playable. But the main issue is that the head tracking just isn’t working. Instead of “can see everywhere regardless of where my weapons point”, the result is “my weapon sight will move according to my head movement”. This is not the result I was expecting.
Aside from that, the mouse movement is still possible. But the point of having a smartphone as some kind of replacement for TrackIR became moot, in this case.
If the game supports TrackIR, which is the case for Arma3, do not use the mouse option in Sensor Type, use the TrackIR option instead… just remember to start the streaming before starting the game (so that Arma can detect the active TrackIR process).
As for USB Tethering, make sure Tethering is established (can take up to a minute or so for Windows to properly detect). You can verify it is up by running ipconfig from command line and see if there is a network with IP 192.168.42.129 and an assigned IP 192.168.42.*). If USB Tethering is working, Triuns Gyre will use it automatically. There are issues with Android devices linked to Verizon and other providers that are specially restrictive regarding tethering.
But if Wifi is the only option, try the hotspot option as it might be faster than going with a connection to the router (i.e. phone connects to PC instead of both connecting through router).