First settlers and migration
If you are dealing with first settlers in a region, remember that in this time period most single people found their spouse within a 10 mile radius of where they lived. If your family lived on Duck Creek, check and see who else lived on Duck Creek and if they had children. You may find the spouse and in-laws you were looking for.
With first settlers in an area, prior to the organization of counties, land sales were read into Circuit Court Records (traveling judges). In remote areas, this was the only way of having a land sale recorded. This was also used for will probates and other financial agreements. Later the Court of Pleas (sometimes a traveling judge) took over these duties.
This brings another thought . . . physical court buildings and/or county clerks were not necessarily available on the date the state decided to divide the county. It may have taken months or years to establish a place and person to record various ‘court’ documents. Suggestion: look for the document in the old county, or if they really sliced-and-diced a neighboring county.
Always remember the distance and the mode of travel available, people did things and went places that were convenient. Wills and deeds may have been filed at the nearest courthouse, not necessarily the on the their county. This is especially true in remote counties.
Most people move from region to region in families, "clans", etc. If you see the same names going from one region to another, they were probably aunts, uncles, cousins or in-laws. (possibly a couple of generations back.) Relocating with other family members is a good reassurance that you have the right relative.
P. S. I will take general questions submitted and try to answer them.