I'm confused. Is an outside hitter supposed to start their approach inside or outside the court?

An outside hitter should always start from the outside. From there, you should be able to see the block and hit either sharp angle, through the seam, or rip line :) From my personal experience, if you start inside, it's easier for you to get blocked, you can start your approach from the inside, but you always want to have those different hitting options to be a very efficient OH.