There are three basic defensive concepts in the NBA. One is man on man advantage/disadvantage, taking an extreme example lets look at Kyrie Irving vs Andrew Bogut. Kyrie is never, ever going to be able to back down Bogut in the post and get up a good shot from that position. On the other hand Bogut cannot guard Kyrie on the perimeter. Irving will be either taking wide open 3s or getting to the rim with ease, and because the offense gets to dictate where and when to start the attack such a pairing will always go in Irving's favor. Before you smack your forehead, exclaim "duh" and wander off to another site there is an important concept to tease out. The gap in skill can be measured by the amount of time it takes to work a good shot. Turn the shot clock off and Kyrie still is going to fail in the post vs Bogut, and unless you cut the shot clock down to under 6 seconds Bogut is not going to be able to handle Kyrie. This is the concept the hedge is based on, a big man steps out on a guard and essentially says "I can handle this space of floor for this many seconds against you" and then he is often in full retreat mode, scrambling back to find the open man.
The second basic concept also applies to the hedge, and it is the power of position. A relatively slow footed C can corral a lightning bug PG if they anticipate the screen, how the PG will use the screen and know where to retreat to recover. The first part of the hedge is to know how long you are guarding the ball handler and the second part is to be close enough and ready to get to the necessary spot before he does.
The third concept is help defense, and the most important part of help defense is knowing where to be. This functionally means that the on ball player can aid his help defenders by getting beaten (when he is beaten) consistently. Obviously it is better to never get beat, but since every one does getting beaten to certain spots, at certain angles is the way to go, allowing your team mates to get there and contest the shot.
This is a very basic intro, but I need a base to build on when talking about the Warriors defense. The Dubs D is based on the switch, and based on the fact that they can switch. When a commentator says "Draymond Green can guard the 1 - 5 spots", they don't literally mean Green can get out on the perimeter and guard Kyrie Irving from the beginning of the shot clock, to the end for 30+ mins a game (at least you hope that they understand some nuance). If Bogut can handle Kyrie for less than 6 seconds of shot clock, Green can probably do it for 12-15 seconds on most possessions. If the Cavs take 6-8 seconds to bring the ball up the court, survey the D and initiate a play then the Warriors will be very close to that time frame where they can switch Green onto Irving without major concern. If they switch before this there are two fears. One is that Irving can isolate and break down Green, and #2 is that the man Curry has switched to has the time after receiving a pass. Having Love and Lebron on the court with Kyrie makes issue number 2 a potential nightmare for Golden State. Either player can beat Curry in the post easily, on multiple possessions a game, while also being able to pass out of a double team if GS decides to help.
Now Golden State wants Curry on Kyrie, not necessarily because he is their best on ball defender (though he is underrated in this aspect) but because their switch based style relies fairly heavily on slowing down early offense and getting their defenders into that window where they can hang on without to much help and use the shot clock to their advantage. Curry being on anyone but Kyrie is an automatic mismatch in some way that should scream out "take advantage of this!" every time down the floor and encouraging that exact early offense they want to delay. Even just swapping Curry onto Shumpert means their best offensive player is at risk of burning energy fighting off a player that is 2 inches and perhaps 35 lbs heavier each time down the court.
In part 2B I will address what Golden State will have to emphasize to avoid the issue of switching early on, and in part 3 start in on what Cleveland will have to do to slow down the Warriors offense.