1) A level 30 player has a good grasp of the power cards and power combos. But they will probably overbuy these cards, failing to notice the times when they aren't dominant or when there are good counters in the way a level 40 player might not. Mr. Level 30 might fail to notice less powerful combos on boards without power cards.
This actually sounds alot more like the difference between level 20 players and level 30 players to me. As a level 30ish player (33 for now), I've gotten here primarily because I can see past the "obvious combo." Most level 20 players can recognize torturer/fishing village, and can beat me if they get good shuffle luck and that's all there is on the board.
2) is a little closer to the truth. I'll notice all of the cards that combo together, but I might not know the perfect order to buy them in, and I don't always accurately realize what my average hand will look like in a few turns.
Let's assume in the torturer/FV option, we also have militia, bridge, hamlet, watchtower, and menagerie. All of the cards could be great in this game. Militia beats up your opponent's hand even more and might let you get to $5 earlier. Bridge lets you get in better buys (but could potentially clog your deck, and militia might be better). Hamlet fits in well with multiple actions and might even be better than FV for consistency (but when do you buy one?). Watchtower pretty much nullifies torturer in any hand that you draw it and combos with FV/Hamlet (but it doesn't always work well with other +draw). And menagerie works great with small hands, diverse decks and Hamlet (but is it worth it with watchtower? and how many do I buy?)
Throwing in a slow trasher might be interesting as well. Remodel? probably not worth it. Upgrade? Nice, but you have to sacrifice a torturer buy, and when do you do that?
I can see that all these other cards would be useful, but it's a matter of knowing which part would add the most benefit. Also, knowing exactly when to start greening might be difficult in a game like this.
On the other hand, I'm great at when knowing to ignore big engines and just go for doublejack, double masquerade or something similar.
Edit: I also agree with DG. Often times I will use an equally good strategy to an opponent but lose because I make a lategame mistake like buying province>duchy>estate when simply eating up the estate pile would give me a win.