In looking at the results so far, it appears that there are a number of different groups, as opposed to two distinct clusters as I had expected to see (i.e., one around the English Baughs and another around the Germans Baughs/Bachs). Within the Baughs from England and Germany, there are several different unrelated families.
A closely related cluster of five samples (FTDNA N73728, FTDNA 154882, Ancestry.com 3, FTDNA 136802, and FTDNA 191421) appears in the R1b1b2 haplogroup. Two of the men in this cluster (FTDNA 136802 and FTDNA 191421) are known to be descended from William Baugh of Henrico County, Virginia. Another (FTDNA 154882) traces his ancestry to a William Baugh (b. 1803-1805, Virginia) who must also belong to the same family as the others. FTDNA N73728 has a 12/12 match with the modal haplotype of this cluster, but I don't have any information on his ancestry. The "Ancestry.com 3" sample comes from a man in Scotland whose earliest known direct male ancestor died in Scotland in 1841. His haplotype is remarkably similar to the others in this cluster (differing only at DYS460 from the modal haplotype), even though this person's line never came to the USA. His most recent common ancestor with Virginia immigrant William Baugh must have lived not long before William Baugh emigrated from the British Isles. Whether he came from England or Scotland will be determined when we can find some samples from other closely related men in the British Isles whose documented line goes back to the 1500s or so. This man in Scotland has a close DNA match with a nephew of Alex Haley (author of Roots) who is known to be a direct male descendant of a white slave owner named Baugh who lived in antebellum Alabama just prior to the emancipation of slaves in the USA. So, Alex Haley is also a descendant of William Baugh of Henrico County, Virginia. More William Baugh (Henrico County) descendants from the different branches of his family are needed in this project to allow us to determine which haplotype markers define the various branches. For example, in sample FTDNA 136802, the mutation of marker DYS390 from 25 to 26 appeared after his line split from FTDNA 191421 in the early 1800s.
Another cluster appears in the G haplogroup family (probably G2a) - the top two rows and possibly the third one. The earliest known ancestors were born in Kentucky in the early 1800s. Their families probably came there from Virginia. Since they are of an entirely different haplogroup (G2a vs. R1b1b2), they are not related (genealogically) to any of the others in the database.
The one known descendant of Bartholomeus "Bartle" Bach is FTDNA 140697. He belongs to haplogroup R1b1b2, but his haplotype is quite distinct from the William Baugh (Henrico County) cluster.
To summarize, the DNA evidence points to the probability of several different immigrants to America in the 1600s-1700s (not just two) from whom the Baughs in America trace their descent. Analysis of y-DNA along with historical records will help us eventually to differentiate the different families. We just need a lot more samples. I appreciate those groundbreakers who have already joined the project.