I don't think he's the best, but I think he's a worthwhile pick in terms of a cheese type support. His abilities can really lock down an AD carry, and his ultimate is a very long range initiate, catching most people off guard, which is what cheese is supposed to do. He is terrifying to lane against, as the moment he hits 6 with his ultimate he can really start dominating his lane against almost all setups.
From my experience, it's the practice. High elo players tend to stick to their guns with what champions they can play, and very rarely stray away to new ones. Professional and highly competitive players are always willing to try new things and new champions that go along with their given role.
As for the difference between the games themselves, is that in high elo, people are less reliant on their team and just try their best to win on their own, they will very rarely make calls such as grouping up or split pushing, and just let things flow. And in competitive games people have genuine strategies they use to win, and of course the players work and communicate together to help winning happen.
I got into LoL because a lot of my friends from World of Warcraft were all over the game, some even quit for it. So I played a few games and fell in love with it, and followed my WoW friends in quitting and moving on.