I've never used necromancy before, so I just created a Breton vampire who will specialize in it along with Destruction. I know that the master Dead Thrall spell resurrects a body permanently, and you can have two. My question is, who makes the best thralls? I'm already going to get Orchendor, because he's supposedly THE best. Didn't even know you could thrall him. So here are a few other questions I have.

1. What is the level cap for thralls?
2. Should I get my thralls before I reach a certain level?
3. Do they have any follower commands?
4. Do their bodies turn to ash when they die?
5. Besides Orchendor, who makes a good thrall?

Vrythur made a pretty good one for me, but you have to plan him out accordingly. I recommend checking the dead thrall wiki pages. They have some great tips there.

1. What is the level cap for thralls?
Not sure what you mean by this? Are you asking what level is "too powerful to resurrect"? If so EDIT: level 40 with necromage perk, 34 without.

2. Should I get my thralls before I reach a certain level?

3. Do they have any follower commands?
Nope. And they get in the way. Good news, you can kill them, and then re-resurrect them. Also, you will lose them if you go to Solsthiem via boat or to Skuldaffn.

4. Do their bodies turn to ash when they die?
Nope, unless they are disintegrated by a lightning attack.

5. Besides Orchendor, who makes a good thrall?
I like Archconjurers, Arch Pyromancers and Volhikar Vampires. They make more NPC followers while in combat making for epic battles, not to mention that they are powerful, and easily replaced. Named thralls are fun, but I am not the biggest fan, I like the dialogue that no-names have. Personal favorite is a http://uesp.net/wiki/Skyrim:Dremora_Markynaz. But you can only have 1 or you risk a bug.

NOTE: transforming into Vampire Lord will dispel all of your thralls.

For me, the best candidates are female Bandit Chiefs with the female animation. ( The ones that don't walk like they are carrying potato sacks around ) Improve their Steel Plate set, enchant it with health, give them some improved and enchanted weapons and let them go.

One thing to be careful about, is if they die while in combat against another Necromancer. They will raise your Thrall against you. Not good...