Funny how things change... Back in the day, we were all taught to use a high wrist, straight elbow technique with our recurves and compounds. That changed when they started dropping brace heights to jack up arrow speeds. People actually HAD to start shooting low wrist with a bent elbow to keep the string from beating their arm to pieces.

The same question comes up with new longbow shooters. You shoot longbows with a low wrist and slightly bent elbow, exactly the same style as today's compounds are intended to be shot. How much is the correct amount of bend? When you put the heel of your hand down on the grip, your elbow naturally takes the correct amount of bend.

Hold your bow arm out straight, but relaxed (do not lock out your elbow!) and keep your wrist straight like you would if assuming a high wrist grip. Now, bend your wrist back, as if you were switching to a low wrist grip. Your elbow will bend slightly. That is pretty much the correct amount of bend for the way your bone/muscle structure is built. Someone else might have more or less bend in the elbow, but that's because they're put together a bit differently.