Hello everyone how to properly RP a DK ?

Is there levels of undead ? I mean why would Arthas bother feeding the DKs if they gained nothing from it. Can they still digest it? And if they can bleed even those with out the blood specialization then wouldn't that mean their heart is beating. I mean they are undead that not really up for debate, I just wonder if its like being resurrected but instead of a priest using the light where they can go on having a normal mortal life its dark magic and so the aftermath is different. They function better than the minions you get in unholy but you're not quite mortal. Its like a weird limbo. But still...better than glittering in the sunlight...like some undead from a different franchise...

I mean I know Sylvanus started off as a Banshee but she got her body back and was able to perma die after words. So she's undead because she died, got turned into a banshee, got her body back, then died, then came back...again but she isn't...like the other Forsaken if that makes sense.

I dont know I'm just confused on the different types of undead there seem to be in WoW lore (from skeletons to elven vampires) and how everyone is interpreting it. I'm not trying to be difficult or anything I'm just trying to make sense of all of the information. The other threads seem to range from like '08 to now and it seems still the only thing people agree on is that a DK died and was risen again. Other than that I'm seeing all sorts of things. Including some pretty...strange things...

Side note: who doesn't want the cool scars that come with these other skin tone options lol