To amke this clear let me ask you this, what makes the difference between helping and killing Great Khans besides losing an option to get quests from them if you chose to kill them. In my first run I chose to help them and I've seen what they offer, so what new experience will I get from killing them all on my second run? Will there be a new set of quests open to me for doing it? Not really, the only thing that will happen is losing an opportunity to take their quests again.
That's a good question. I'm not sure about the Great Khans having diverse experiences that await ... although playing through their camp with three different characters, I found new quests each time

and every character had at least one unique experience in resolving them. My peaceful character never killed off the Fiends, so she was able to do the drug runner quest. My gunslinger character discovered Melissa's quest to fetch the briefcase that my peaceful character missed. My violent character (my first) was allied with the Legion, so she basically took a quick look around and then left, it's true.
But let me suggest that using a different approach on your part can make things very fresh. When my violent character got to the Tops,
Spoiler she refused to relinquish her weapons, something your middle-of-the-road-befriend-everyone character would never do. The ensuing bloodbath was a great chunk of gameplay and when it was over I found that Benny was long gone. I never saw him at all until I got to the Legion camp.
I told myself at the beginning of the game, when anyone mouths off to this character, she kills them, and I followed through with it, which resulted in this exhilarating and really fun sequence and several others like it. It was great.
Ever tried going through Vault 34 without firing a shot? My peaceful character did it. Her idiom for the entire game is to never hit the attack button or open VATS. She's made it to level 26 so far. I'm here to tell you, it's not the same game from a new angle, but perfectly playable and loads of fun.
What changes in your behavior did you decide on for your second playthrough? Did you just make the same well-rounded character again and say, OK, now I'll do it all all over again and pick different speech options? Or did you have some kind of idea in mind on how you would do things really
differently?