Expected goals shouldn't be treated as actual goals. It is really only showing you how many quality shoots on goal you had and when you combine it with its inverse, you get the xgf% which is useful. xGF IMO is being overused throughout hockey because it offers a simple stat to show shot quality for and against. It is only one metric and without context it becomes like any stat, meaningless. I would guess that Doan is generating more shots in high quality areas where as Peterka has a better shot overall. As you say, it is about how they create offense.
Idk if you mean if Doan is worse or Peterka is worse but still puts up 25g. The issue wouldn't be the 25g either puts up but what the split looks like. If I put up 25g but allow 45 because I don't suppress shots in my own end, the 25g really doesn't matter. Dylan Cozens is a good example of this.