Okay so a few comments
1. The side that was sinking the world is the evil side. Plain and simple. I don’t know what Vegapunk is even talking about. (The morality is gonna be extremely OBVIOUS, the ancient kingdom will be the “bad” guys simply because they MADE the ancient weapons, not because they used them to sink the world. The obvious bad guys here will be the people WHO FUCKING SUNK THE WORLD)
2. How do Greenbit and Dressrosa work? The tontatta have information from before the void century. The Donquixote family ruled Dressrosa UNTIL 800 years ago when they went to Mariejois to become celestial dragons. That means they ruled over a MASSIVE Dressrosa that kept sinking more and more throughout the huge war until it was just the island left. That means it’s likely Greenbit and Dressrosa were the probably part of the same country. They were like two peaks of the highest mountain or something in the larger Dressrosa kingdom
3. Again we know the Tontatta history with the Donquixite family from the void century. We know they were evil even back then. That means WE KNOW the 20 kings were the evil side of course. The fact that Nefertari were also on the evil side shows there was obviously some lying going on.
4. Imu (or one of the 20 kings) started the war by using the ancient weapons for violence (remember we are told the ancient weapons were not necessarily created for violence, they had other uses in the past). But since the ancient kingdom was the creators of the ancient weapons, they got blamed for what Imu did. That’s how Nefertari kingdom ended up getting tricked into joining the 20 kings, they were lied to. And then when they realized the lie, they joined the ancient kingdom in secret to pass on the will of D.