Some very initial thoughts (open to criticism and revision) on how I see things so far in relation to Greeks:
1) Eastern Imperial Romans, the direct progenitors of the Byzantines, being heavily Anatolian: no surprises here, I don't think it holds to dispute that the Byzantine Empire was largely (if not entirely during some of its periods) a Greco-Anatolian historical project/entity, Mithridates Eupator VI of Pontus having an honorary mention as partly responsible!
2) R-L584>R-19434>R-R12332 found in a lot of Urartian samples leaves little to imagination? As such, modern Greeks, and especially Pontics, with L584 are probably Byzantine or Hellenistic lineages of Armenian or other South Caucasian/Iranic (Medes) origin. Again, no big surprises either given the historical relation of the Greek world with the South Caucasian peoples.
3) This is the point that I am certain I am going to get a lot of flak for, but as I said in the opening sentence, I am still trying to connect the dots. From what I gathered from the little I spent on the E-V13 stuff and the relative discussion, this seems to be a Thracian related hg and a Medieval bloomer in Greece, no presence whatsoever in the ancient Greek samples? If so, then chroniclers like Chacocondyles are vindicated when they wrote about the mass medieval migrations of the Vrachs/Vlachs in Epirus, Thessaly and the Peloponnese, referring to them as a nation of Dacians, "the relatives of the Triballi and Moesians, the Illyrians and the Croats, the Polanians and the Sarmatians (Chalcondyles, 1556)". Given how successful these lineages are in modern Greece, Vlachs seem to play a pivotal role in the formation of the modern Greek ethnos, something that is corroborated by ethnography and history.
Just my initial 2 cents. So far, Byzantine and Ottoman historiographers are having the last laugh.