I can't help you with your specific questions, but I can tell you the following:
My ancestor David Wherry (as the name in my family line has been spelled since the early 1800's) came from northern Ireland about 1718 and settled in Chester County, PA. Some of his grandchildren moved to Washington County, PA. However, there was another Wherry family in Washington County, who as far as I know were unrelated.
The surname of my ancestors was spelled various ways during the 1700's and early 1800s, including Wherry, Wharrey, Wharry, and Warrey. It would not be surprising that some of these alternate spellings survived down to modern times.