Guess you don't have much to worry about then.
As for "Tilling", There are several different plows that turns the ground in different ways.
Regardless of how it is done, some people call it tilling.
If it turned the top layer under and left the lower layer on top, then it was a "turning" plow.
This can be done for a few inches deep to over a foot deep.
The red clay type soil that ends up on top is the subsoil.
But, as I can tell, you know that.
there is so many different types of soil across the country, it is hard to compare as to what and how "plowing, tilling, discing" or how ever the soil is worked, or condition the soil, which ever one prefers to call it.
Of course, you know all about that too.
So there isn't much I can help you with.
Maybe these other people can give you some tips.