I agree with much of what you've said. I will have to take your word on Fort Mill's talent since I haven't seen them play, but it's clear from their record that they are one of the best teams in the state. I've looked at the brackets, but it's still hard to determine when teams will meet with one another. If Mann and Fort Mill hit no bumps in the road between now and Upper State, they should meet there. But, one of the two will have to face Wade Hampton early on and the other will face Dorman. Wade Hampton is good this year, and it will be interesting to watch them in the playoffs. They had a good team last year, but, if I remember correctly, they were without one of their top scorers during last year's playoffs. Dorman is good too.
As far as the home field goes, that is an advantage for Fort Mill. The turf may also play to their advantage, although Mann does have quite a few ECNL players who see turf quite often. I think that the faster team is usually the team with the advantage on turf. I'm not sure if that is Fort Mill or Mann, but Mann does have it's share of fast players, provided those fast players who are used to playing on turf are on the field for much of the game.
In the end, much in high school comes down to coaching and getting the right mix of players on the field at the right time. Most high school teams rely on the neighborhoods that feed into the school, and it's up to the coach to make the best of the mix of talent they are given. Wando is a huge school in a soccer rich area with a coach that is successful in both club and high school. They have the state championships to show for it. It will be interesting to see if there is a new team (either Mann, Wade Hampton, Fort Mill, or Dorman) that will take that championship away from them.