I have exactly the same config.
Garrecht Air Avionics send trafic to my G3X.
But in order for SafeSky to work properly, you need to cut the WIFI from the tablet to Air Avionics. This is because your tablet connects to Air Avionics’ WIFI network, which does not have mobile Internet access. This means that SafeSky will not work.
While SafeSky is compatible with SkyEcho, Pilot Aware and Satrtux, it doesn’t work with Garrecht. If you ask them, it’s on their side.
So to date, there is no possibility of coupling with AirAvionics.
Personally, the difference in traffic perceived by one and the other is indisputable. SAfeSky gives much more information than Garrecht (from my own experience), but having the two working in parallel is always a good thing. That’s what I do personally,