I don't think you'll find any neighborhood with a "large" Indian population in Fort Mill, though there are quite a few Indian families in my neighborhood with homes in your price range.
I would suggest looking into: Fallbrook, Balmoral, Summerlake (town homes) - these are all part of the Regal Manor HOA and in the Northeastern most area of Fort Mill, on the NC border and Lancaster County border.
We always hear fireworks around Diwali and have a few neighbors put up lights
And the cub scout pack that my son belongs to has 3 or 4 Indian families that I know live in our neighborhood.
We're in Fallbrook.
Hope that helps!