Hello Javier
we are using iPads as EFB-units, so we also have a COTS-unit. for the number of channels, you may want to scan through:
https://discussions.apple.com/thread/1690081?sortBy=best
Not as an official source but to get an idea.
As we were not able to proof the data for the 12 channels so far on the internal audit we were forced - at the moment - to NOT allow the ownship position - although I personally see it as a definite improvement to one's situational awareness – If used alongside rigid procedures and clear understand that the position indicated can NEVER substitute a clear look-out and verification of one’s position.
We are trying to get support from the application vendor, so far we are not there yet.
YES, I think EASA should reconsider their position IF the operator has proper procedures in place.