According to N.O.C. Vol 1 pg. 91, Archibald went to Georgia by 1759 with 2 kids. In N.O.C. Vol 2 back of pg. 76 she mentions a petition for land in Georgia by an Archibald Offutt for himself, wife, and two children. Probably he was born before 1737, as an Archibald Offutt was a petitioner in 1751, you would have to be an adult to sign that.
According to Vivian Mettee; Archibald moved to Georgia after he was granted land there in 1759. He moved to the land which was on the Savannah River near Worthington's Bluff (Believed to be near present day Augusta). Vivian uses as a reference "A Journal of the Governor and Council of His Majesty's Province of Georgia commencing the 8th day of March 1759".
Vivian further states that Archibald later moved to the Edgefield District of South Carolina, and is buried there. She believes that Dr. William Johnstone Offutt was one of his 2 children.