” By the time of Yorktown, he was a Captain. Of Militia or Continental Regulars, I have never learned.”
Your GG+++ may have been both, like one of mine was. I had an ancestor at Yorktown who had been a Continental Regular until Valley Forge. But at Valley Forge George Washington took the opportunity to reduce the number of officers and he was one of them. This guy then went on to be a Colonel of Virginia militia which is what his role was at Yorktown.
Militia Colonels usually had held a different (lower) rank when they were Regulars. Good records from the Revolution can be hard to find. My ancestor shared his name with another man from the same city in Virginia- they appear to have been cousins- and they both were in the Revolution. Sorting that out their history was a chore. But the other fellow was a good deal more prominent so that was a help in figuring out whose record was whose.
Mine went on to establish a land grant in the far west , as a reward for his long services in the war. That land grant went on to become what is now Gallatin Tennessee. His name was Capt.James Trousdale.