Mercule
Adventurer
A bit of both. Ecologies tend to have their major players in balance. There may be outliers in any area, but there's a reason it's stable.
What that means, in play, is that any given "dungeon" will tend to be homogeneous in CR (i.e. within bounds of "tailored"), but the players should always be cognizant of surprises (oh, look, the lich just wants to be left alone). Also, they can certainly find dungeons that are well above or below their capabilities (though I never underestimate cunning players), there will always be clues about the general difficulty (I wonder why no one has retrieved the sword of killing gods before now) and/or a bit of gentle nudging on my part.
What that means, in play, is that any given "dungeon" will tend to be homogeneous in CR (i.e. within bounds of "tailored"), but the players should always be cognizant of surprises (oh, look, the lich just wants to be left alone). Also, they can certainly find dungeons that are well above or below their capabilities (though I never underestimate cunning players), there will always be clues about the general difficulty (I wonder why no one has retrieved the sword of killing gods before now) and/or a bit of gentle nudging on my part.