I haven't had access to the Ravenloft book, but as of the UA at least the intent is that the Dhampyr "lineage" completely replaces the characters "race" and any features it may have. The first level feat is the principle racial feature of variant humans.
Allowing them to get a whole race's worth of new features on top of getting a feat would be pretty overpowered. I'd only allow it if everyone was getting a first level feat or if I was in some way severely penalizing being a Dhampyr in the setting.
Thanks Benjamin. I agree but it has changed significantly since the UA. As I read it, the racial ability bonuses are replaced by what the Dhapyr gets and you can replace other racial features with two skills of your choice, but it does not mention feats, only movement speeds skills. It also specifically calls out languages and senses. Dual type is also gone.
Kind of what I was thinking if the first sentence on the Dhampyr is intended to read that all other features of your race disappear. So if you're Dragonborn then the breath weapon wouldn't work anymore either. It actually specifies that in a sidebar.