Ashkenazi kohanim and Sephardi kohanim have the same male DNA.
Gaon: The 50% conversion rate to Christianity is a historical figure known to Klal Yisroel for centuries. It isn’t under dispute or controversial. (Incidentally, I think secular accounts also use this approximate figure.)
Regarding Reform, intermarriage and commitment to Yiddishkeit, the weak among the Sephardim already converted to Christianity, so the Sephardim that are left are the strong ones in terms of Yiddishkeit since their weak already left. The Ashkenazic weak left Yiddishkeit hundreds of years after the Sephardim, when the Reform/haskala came to town.
There are many millions of more Ashkenazim today than Sephardim.
None of this, unfortunately, is shocking. 80% of Klal Yisroel was wiped out in Eretz Mitzrayim during the makkos, for being too weak in Yiddishkeit. And when Moshiach comes they’ll be another cleansing with 80% again being wiped out. The seforim say this.
Regarding the looks, who is to say whether the “Ashkenazic look” today closer resembles the look of Yidden during the time of the Beis HaMikdash, or if today’s Sephardim are a closer semblance. No one knows. Assuming even there’s much of a difference in looks. Frankly, most people couldn’t tell whether a Yid is of German Ashkenazic extraction or of Syrian Sephardic extraction, if both are wearing the same black Borsalino and suit.