Thanks for all the answers. I learned a huge deal myself. I admit I made a couple of terminology mistakes myself in the question, which veered off the discussion a little bit.
However I’m looking for a practical aspect of the system. To re-iterate:
1. Does each RNAV system comes PRE-set to work with only one GNSS system. If not, does pilot has any control over it to select which one to use (e.g. switching from GPS to Galileo).
2. Is there a automatic switch between GNSSs in case of failure in one.
If you can specify systems you’re using that would be an awesome direction for me to make further research.
Again thanks for the answers. Cheers.