I would assume the answer is "yes" for the FrSky Taranis without modification, "yes" for the Turnigy 9X and 9XR radios with modification, and "no" for Spektrum radios. The Spektrum radios are a closed system and modifications are unsupported and highly discouraged.
The FrSky Taranis has a USB port that could be used for bi-directional communication Ardunio and there is a Smart Port connection in the battery compartment. If you just want to do what the Companion9X does, you do not even need to modify the Taranis firmware. Otherwise, you will need to reprogram the USB interface portion of the Taranis.
The Turnigy 9X and 9XR does not have any bi-directional interfaces available. It is theoretically possible to modify the radio to provide a suitable interface. If you only need a unidirectional interface, then you could use Trainer port but using the module for this purpose means you would not be able to have a transmitter to control your plane. In any case, no matter what, you need to change the firmware (which on the Turnigy 9X requires hardware modifications).
What is it that you want to do with an Arduino? I might be able to be more helpful with a little more details.
Umm... Ok, I understand using the OrangeRX Module to control the Nano QX. I do not understand how you intend to use "an Arduino mega and an external pixy camera for positional feedback." The Nano QX has an integrated unidirectional receiver (as far as I know DSM2/DSMX is unidirectional but I could be wrong) so any positional feedback has to be done with a separate radio system. Given the separate radio system, I do not see why there is a need to have the 9XR interface to the Arduino mega.
Also, the Nano QX is a very small aircraft with very little payload capability (I think they discourage having any payload). So I am not even sure it can carry any sort of camera, let alone enough gear to provide positional feedback. I will be surprised if you can some how to make it work and would love to see video and photos of your final working solution.
The positional tracking is with two (or three) Pixy cameras (eyes) attached to the arduino mega (connected to the tx).
This is for learning to control quad motion with external feedback in a controlled environment.
If I understand where you are going, nothing would be on the Nano QX. You would have camera watching and tracking the Nano QX and the Arduino would be some how impacting the control signals being sent to the Nano QX.
If this is the case, you can have the Arduino send control signals into the Trainer port to be mixed in the Tx before it gets sent to the Nano QX. Or you can put the Ardunio between the 9XR module port or trainer port and the OrangeRX Module where the Arduino is what actually sends the commands to the OrangeRX and can do the mixing or automated control.
If you are doing something like the second option, you really do not need any Radio or you can use any radio (as almost all can provide some sort of trainer output) and the Arduino can control the OrangeRX module without any radio.
This is great news. All I need to control multiple nano QX quads will be the same number of OrangeRX modules connected to arduino mega. The Pixy camera has the capability to track multiple quads.
This could mean nano QX quads flying in a formation like I watched in a TED talk. This opens up new possibilities.
Assuming you get the JR style module the info is really easy to find:
From the top:
Though I believe the ANT connection isn't used on the orange DSM module since it has it's own antenna port and if you'd be using just the module you'd probably just want to use the antenna port on the back anyway.