Hi grovierogue and welcome to the forum.
1. Vampires can eat regular food, but they get the nauseous moodlet and it doesn't raise their hunger bar, so plasma and plasma fruit is about it. I am not sure about the plasma fruit pancakes, it has been a while since I had one eat those.
2. Too much sun, of course, will fry a vampire, unless they have the sunscreen. After six pm, they skill a little faster than during the day.
3. You do have interactions to hunt someone, feed on someone, turn someone into a vampire, read someone's mind, learn traits and make someone think about them. You click on somebody else to do that.
4. They don't sleep in coffins, but they have slabs in the buy mode, but they can sleep on regular beds.
I am sure someone else can remember more, that is all I can think of off the top of my head. Feel free to ask as many questions as you like. Happy simming.