I won't say that root canals are necessary for crowns but it's better to undergo root canal
before having a crown over that tooth because for a crown to be given on a tooth, that tooth needs to be prepared or reduced in size. So there are chances that the tooth later in time might become sensitive. To prevent that, it is asked to have a root canal done first. And there are no health risks with it, it is a routine dental procedure and is performed very frequently by the dentists all around the world.
Now, for your other query regarding protruded teeth, I would suggest braces over esthetic treatments because with the orthodontic treatment your teeth can be aligned in most natural way.