The Injustice comics mainly stick to their own plot development and don't offer a thorough account of the games. However, there could be occasional references or crossovers, but it's not a full coverage.
Yes. Even if you're not into fighting games, the story can be quite appealing. It has all the elements of a good superhero story like drama, conflict, and character growth. You can follow the story without being overly invested in the fighting aspects.
It depends on your preferences. Some people think it's great for its intense storylines and well-developed characters. Others might not be as impressed.