I live about an hour and half from Stringfellow, but haven't been there yet.
For topography, I'm very certain it's all flat since it's only minutes from the coast.
Just looks to be densely packed with trees.
As for ATVs, the TPWD public hunting sheet says that ATVs are recommended, but I'm not sure why since it's not very big. Then again, I can handle long walks.
You can use hand carts. I hunt solo often as well.https://tpwd.texas.gov/huntwild/hunt/public/annual_public_hunting/resources/716.pdf