Hmm. Alright.
First, to address the elephant in the room, Delphi has two designated Droyne populations.
-Ewoin (0202) is shown as a Droyne World, Interdicted, and low tech. Scout Interdict, most likely, and for their protection. Hundreds of millions of them, balkanized.
-De Rome (0516) does not indicate a percentage, but the fact that De Rome is also a communications hub, has a top ranked port, significant Imperial nobility, and is also Balkanized, suggests that the lack of unity is Droyne-specific. One of the nations here is Droyne, and are staunch in their separation. That doesn't mean they are all separate, but most probably are. This scenario argues for no specific percentage of the populace, though I tend to think that less than 15% or so seems unlikely.
Neither world is ideal for Droyne and neither is flagged as an Ancients Site, so both are likely refugee worlds dating back to the Final War, or had their Ancient presence erased aside from the populace.