Your describing what is usually referred to as "quarters" or "2-High Robber."
To answer your original question, its a boat load. There are all kinds of ways to play zone defense and not all kinds of "cover 2" are the same. In reality, the so-called "tampa 2" really isn't cover 2 all the time, it turns in to a 3 deep zone defense vs multiple vertical stems to the same side. To really simplify things, it basically comes down to how the defense is going to try and defend 2 vertical routes to the same side. You can't just squat your corner and have your safety be responsible for half the width of the field, especially in the league, because the safety can't cover that type of ground. So the variations come into play in how different teams try to take care of the 2 vertical receivers. Some will pattern read their corner off #2, so that if he goes vertical, than the corner will lock on to #1 and the defense becomes a quarters variation. Others will have the OLB wall off and carry #2 if he goes vertical and let the safety run over the top to #1 and keep the corner squatted. The tampa variation has the ILB responsible for getting to the seam route by #2 with the safety over the top and the corner and OLB staying put. That is, in essence the major variations, but there is certainly more to it than just that.