He is not a twin by birth, either they were both manufactured at the facility on God Valley or he is a clone.
He is going to be the equal of a younger Shanks with probably either scientific augmentations to his body or additional training in the techniques traditionally associated with the Marines/CP. I doubt he will show similar Conqueror haki because I don’t think that is a genetic trait although it is possible. My intuition is that he will either be a powerful pseudo-Shanks or that he will pull out something totally different like a weird Paramecia devil fruit power just because Oda.