Can one simulate a top GM strength? I would like to know roughly if a top GM could win a given position against a top engine.

Is there a way of adjusting an engine's settings to simulate the strength of a top GM in order to make it play against a full specs engine? If so, which engines allow for these adjustments?
Ubisoft's Chessmaster: Grandmaster edition allows you to set games between artificial players. One is the engine itself and there are simulated top players, e.g. Anand. You can set the games from the starting position or from a set position.

Please see my answer to Looking for a good chess program with a couple of features for relevant screenshots.