Will traders respawn if i kill them?
What about if an Ai kill them?

People like Knight Torres, and the Van Graffs will never respawn unless you are on a PC. Not sure about roving traders, but there is a lot of them.

I believe all named traders will remain dead, no matter what way they were killed. It could be you, a pack of Deathclaws, or a Legion Hitsquad, but once they are dead, they remain dead, unless you play on PC and can work with console commands.

I know for a fact that the named traders die for good.

The roving traders? I don't know, because I don't kill them.

Ok thanks for help.