If an effect works on at least one of a creature’s types, that effect can work on that creature. For example, if you are both a Humanoid and an Undead, cure wounds works on you, since the spell works on a Humanoid.
Everything so far is peachy keen. I was going to introduce an NPC that is a Dhampir Cleric, but ran across an odd edge case. If the cleric uses Channel Divinity: Turn Undead I'm not sure what happens:
Channel Divinity: Turn Undead As an action, you present your holy symbol and speak a prayer censuring the undead. Each undead that can see or hear you within 30 feet of you must make a WIS saving throw (DC 14). If the creature fails its saving throw, it is turned for 1 minute or until it takes any damage. A turned creature must spend its turns trying to move as far away from you as it can, and it can’t willingly move to a space within 30 feet of you. It also can’t take reactions. For its action, it can use only the Dash action or try to escape from an effect that prevents it from moving. If there’s nowhere to move, the creature can use the Dodge action.
I know it is play test material and will have weird edge cases like this not hammered out. I also know at my table I will have to make a call if it comes up. However, as it stands, the NPC is an undead within 30 feet who can see and hear itself, so RAW would have to make the roll, right? And what would it mean if you failed it and became turned and had to move away from itself? What would that look like?