The recommended setup is exactly the same as if you were using an Asobo aircraft with the GNS530, this goes for both PC and Xbox versions.
As far as the PMS50 GTN750 and TDS GTNXI go, I would suggest asking them for any support as they are integrated internally for the Camair 480 using a default setup with a flick of a switch - That switch disables in the code any working functionality of the other two GPS units that are not active(Hence, why it needs to power back on).
Also, I have heard issues recently of the WTT not being able to find the satellites and thus making the GPS null in multiple aircraft. I know its not my plane, but I will look into it for you and reply if I find anything. If there is something on my end I need to do to make it function correctly, I will address it in an update.
For PMS50 the Camair 480 was the 1st plane to have the WTT native with the GTN750 mod. I hope that explains it for you. I flew the Camair 480 yesterday and tested all 3 GPS units and didn’t have any issues, but that doesn’t mean there might not be any. If you have any other questions, feel free to ask.
Edit: I looked into the GNS530 Satellite issue and found that some users just needed to update the GNS530 mod to fix the issue. I found that here in the forums, but it was hard to find.