Halachically there is no difference between Sephardim, Ashkenazim and Mizrachim however in DNA testing there’s a seperate catogory for Ashkenazim and Sephardim. I’m not sure how accurate these categories are since there were many Sephardim that never left Europe since the Spanish and Portuguese expulsions and there are Ashkenazim who lived in EY for centuries so I can’t imagine it is all black and white. Also, the expulsion of the Sefardim Jews did not happen too long ago in terms of affecting genetics IMO.
But, l’maasoh, there are different categories when DNA is tested.