So on one of my older characters I randomly came across a broken cart full of goodies with a Khajiit body nearby and thought it was a bit odd as there was nothing around that I could see at all.

Then with my latest character at the start of the DB quest when you're told to introduce yourself to everyone and they're all standing around talking about their latest kills and stuff one of the guys (I think Astrid's husband) says he killed a Khajiit who was like a kung fu master lol

Could the dead Khajiit I found be the one he killed? Do any of the other Assassin's kills show up anywhere in the world? Like people that for sure have been assassinated by the DB?

if i'm not mistaken, that wagon was located very close to a giant camp.

I've found a couple, except there were burn marks on the ground as well. I think its implied that it was a dragon attack.

this. i have seen that one near a giant camp.

And there's also a dragon's nest near.

The scene is found on the roadside while one is heading westward into The Reach from Whiterun, yes?

Fixed encounter. Nothing special.