Freedom of answering because you choose to speak with your main to change minor things ?
If this isn't freedom for you, to change from minor to big things, because your choices affect everyone around you in some way. I don't know what else to tell you. If what you want is already start doing choices that will affect the whole world like some legendary hero when you just started a game, I... have no idea how to respond to that too. And if you think your Tav is nothing, that on you. I think my Tav is amazing and so far my favorite character in the game.
Well, if such an empty character is your favorite that's up to you.
Shadowheart with his artefact does not impact the whole world. And if the artefact was in Tav's pocket for a reason we'll discover later it wouldn't have changed the world. Just the story of the artefact that would have needed to be a bit more different.
If you were the only character to make those dreams and have those powers, it wouldn't change the world at all.
I don't even understand why you're talking about legendary heroes.
Your Tav is not amazing. He's just the same as every origin character. He has the exact same story except that he does not have any side story. He's not special at all in Larian's campaign, he's only in your head.