Really, augmented doesn’t do anything on its own. It just indicates the creature’s “mechanical history” so to speak. If you read the description, the closest it ever comes to describing an effect is
A creature with the augmented subtype usually has the traits of its current type, but the features of its original type.
That’s all augmented does: it suggests that it might have features usually more associated with the former type than the previous type. Since type changes are always the result of some specific effect—usually a template—ultimately the actual things that the creature keeps and loses are up to that effect, and not the augmented subtype.
That said, in a lot of cases, it can be wise to treat the augmented subtype as meeting qualifications for things. Not targeting effects—too many places note that type changes prevent that to believe it wouldn’t—but things like feats and prestige classes often make more sense when the augmented subtype can meet them as well as the original type. That has to be a DM ruling, though, on an ad hoc basis; it certainly isn’t in the official rules.
By the way, absolutely none of this matters for hold person—as that’s a mind-affecting spell, undead of any stripe are unaffected because all undead are immune to mind-affecting effects.