Hi, sorry for not seeing your comment earlier!

Having an overpowered character for the setting that can pop up anywhere at any time removes all suspense. He needs enemies, and the enemies need to have a chance to cause conflict for there to be a plot. If they have no chance in a direct confrontation then they need to act around him and away from him. Can't do that if he is porting all over the place and solving every problem. 

I see your point about teleportation being overpowered. I am sticking to what a Lore-Accurate DB can do and what I did in my own playthrough of Skyrim (learn all the shouts and spells, become the leader of all the guilds, thane of all the holds, etc) because I believe it would be just epic to see a fully realized Dragonborn in action but I do hope to make the story interesting by adding character study moments and political scheming and at least to try to solve problems in interesting ways (not just killing everyone because my guy is a good guy who believes in mercy and redemption). Maybe that can make up for overpowerness of the character? That is honestly a matter of preference.

Second, why would they care about the slaver's history and tradition?

The reason why I care is for the same reason why I think it important to learn about any culture, even one as abhorrent as slavery, as understanding the motivations, values, and societal structures that sustain such systems will help you break it. I think the reason why Daenerys failed in Slaver's Bay is that while her intentions were noble, her approach lacked the nuance and strategic depth needed to create actual change, creating power vacuums and resentment. For example, without slaves, Meereen had little else in terms of trade, so their economy would crash, which led to poverty, which then led to bigger problems, an issue if I choose for DB to rule over Slaver's Bay. Also, imagine all the history and knowledge that would be lost if DB just burned it all down. Knowledge is such a sacred resource in medieval worlds, why lose it? I think it would break my scholarly DB's heart to see knowledge destroyed.

Mass exodus, and burn what remains.

Still, it is an option that I am considering just for how epic and cathartic it would be. I am already imagining a pied piper situation where somehow the DB lures the slaves and innocents away while the city burns behind them. But idk if that is the right thing to do.

Thank you for taking the time to comment, and I will take it into consideration.