I mentioned elsewhere that Emerald told me that the X20 ships with D'Addario EXP 12-53, but they didn't say whether they were 80/20 or Phosphor Bronze.
I've never been a big fan of EXPs - they feel rough under my fingers - so I'll probably be trying others as time goes by. First choice will be Elixir Nanoweb PB, as that's mostly what I use on my other acoustics. D'Addario Nickel Bronze is another candidate - I have a Washburn jumbo that just lights up with these, and I have a suspicion that the X20 might rather like them too.
I have a set of each, sitting here ready to go
Patience, David, patience...