Since 'lemon' fanfic is inappropriate, we can't really discuss the characteristics in that context. But in general, aang is known for his kind - hearted and adventurous spirit. Toph is strong - willed and independent. In proper fanfic, these traits are often explored in their relationship, like how aang's optimism might contrast with toph's more cynical view at times.
Yes, if the title 'aang is a firebender fanfic' is to be taken literally, then aang is likely a firebender within this fanfic. However, without actually reading the fanfic, there could be some sort of plot twist or alternative interpretation that might make it not so straightforward.
One possible reason could be his strong moral and spiritual beliefs. Aang is a very spiritual character, and his culture and upbringing might have instilled in him the value of all life. Killing goes against his principles of peace and harmony.
He could meet his future self. It would be an interesting encounter as he could learn from his future experiences and wisdom. Or he might meet people who have studied his past adventures and see himself through their eyes.
The 'Avatar Aang' cartoon stands out for its rich world-building. It has diverse cultures and beautiful landscapes. Also, the themes of friendship and responsibility are handled really well.
One of the main challenges Aang might face could be Azula's resistance. She's a proud and powerful character. She may not be willing to accept Aang's help at first, seeing it as a weakness or a ploy. Also, her mental state is complex. Aang has to deal with her past traumas and her deeply ingrained ideas of power and control.
Maybe Zuko has his own goals that don't involve chasing Aang. He could be more focused on redeeming himself in other ways, like helping the Fire Nation people or learning about different cultures without the need to pursue Aang.
Possibly they are random villagers who were caught in the crossfire of a conflict between different bending factions. Aang, being the Avatar and a symbol of peace, feels responsible for burying them and ensuring their spirits are at peace.