I haven't been able to identify a specific "Vlach" J2b-L283 cluster, but according to scientific studies, after the Albanians, Vlachs have the next highest J2b-L283 frequency at roughly 8-10%. If we look at Greece, J2b-L283 peaks in frequency in Thessaly, NW Greece, Euboea, Corinthia, at roughly 6-8%, on the other hand it seems to be close to non-existent in the Greek Islands. So this suggests it peaks in the areas where Vlachs and Arvanites are known to have settled.
J2 grouping at FTDNA is probably a bit outdated but I'll look at Greek haplotypes closer one of these days and report back. However, I have run into a few Greek haplotypes who belong to the same subclades as Albanians, like PH1751, Y23094, Y21878.
Obviously, I'm not implying that all Greek J2b-L283 is of Albanian and Vlach origin, but the above mentioned data suggests a good amount of it is. This raises the question if there was any J2b-L283 among Mycenaeans. My guess is that if they had any of it, most likely it will not be under Z1296, as I currently see this branch having a center of diversity in the western Balkans. And therefore any Z1296 there would be a later arrival, Dorians, Illyrians, Thracians, and later Vlachs, Albanians.
I'd theorize that if Mycenaeans had any J2b-L283 it will probably be upstream of Z2507, as those subclades seem to have more of a Mediterranean spread.
As far as Z631 goes, I still struggle to come up with a main theory of where it could've expanded from. Its TMRCA is only 2900 ybp, and it seems to be present basically throughout Europe, with a significant presence in NW Europe. But considering that it descends from Z1296, my guess is North Balkans and some of it may have been absorbed by the Celts, and later probably spread by the Romans also to places like NW Europe. The Tatar (Eastern Europe cluster) so far all belongs to Z631>>Z1043>>Y12000, so it seems to be a recent Middle Ages founder effect.
Just wanted to say this was written over 5 years ago here, and before we had any meaningful aDNA. It's precisely what we got in Mycenaean Greece
