Annie is often depicted as a more reserved and calculating character. She keeps her emotions in check and is very strategic in her actions. Mikasa, on the contrary, is more passionate and driven by her love and loyalty. She is protective and doesn't hesitate to jump into action when needed.
Yes, there are quite a few. You can start by looking on popular fanfic platforms like Archive of Our Own (AO3). There, you can search for the 'Annie x Mikasa' pairing within the Yuri genre. Some fanfics might focus on their relationship in an alternate universe setting, where they could be in a different kind of society or situation that allows their relationship to develop in a Yuri - themed way. Others might explore how their personalities, which are both strong and complex in the original series, interact in a romantic context.
Well, for one, it combines two very distinct characters. Annie is often seen as more reserved and calculating, while Mikasa is extremely protective and loyal. In a Yuri context, this creates a really interesting power dynamic. Their relationship in these fanfics can be a fresh take on the typical relationships seen in fanfiction. Also, it can explore different aspects of their personalities that might not be fully explored in the original source material when it comes to romantic relationships.
Well, Annie is a very intelligent fighter. She can transform into a Titan which gives her an added advantage in combat. Mikasa, though, is an ace in human form. She's quick, agile and has great reflexes. In a battle of wits, Annie could try to set up traps or mislead Mikasa. But Mikasa is not one to be easily fooled. When it comes to strength, Mikasa's skills with the blades are deadly. If Annie transforms, Mikasa might be at a disadvantage at first but she could quickly figure out a way to counter. Overall, it's really hard to say who would win.