1.) As I see it the personal story is meant to be played alongside leveling, it has a natural flow since you visit places where leveling leads you. Exploring and leveling makes you familiar with a location, when you enter the personal story mission on the recommended level (it's indicated in the top right corner) most of the time you have leveled in that area. Now when you enter the PS-mission you experience this place with a new flavour. If you are higher in level you will get scaled down to the mission-level and everything is fine.
It would make no sense to play the PS without the leveling, since you need an appropriate level to enter the mission anyway. There might be a design problem with the game since it doesn't consider a race leveling in another race's areas. This, I agree, would feel a bit odd, if you don't know the area where your PS takes place.