One great fanfiction in this theme could be 'Trunks' New Heart'. It beautifully depicts Future Trunks' journey of falling in love with a Saiyan. The author does an amazing job of exploring his character in the context of new emotions.
A common trope is the 'forbidden love' aspect. Since Future Trunks has a lot of responsibilities and his situation is often complex, falling in love with a Saiyan can be seen as something that goes against his duties at times. Another trope is the 'power couple' idea. As both are Saiyans or related to Saiyans, they are often depicted as being extremely powerful together, both in combat and in their relationship.
One interesting fanfiction could be about Future Trunks exploring new time - traveling adventures. Maybe he discovers a parallel universe where the Z - fighters have different powers and he has to adapt quickly to survive.
Gohan would be a great character to pair with Future Trunks. They are both strong and have a deep connection to protecting the future. Their combined power and intelligence could make for some really exciting storylines.
Well, there's a fanfic called 'Trunks' Time - Travel Tales' that's really good. It plays around with the concept of Trunks' time - traveling in a very creative way. Then there's 'Future Trunks' Love Story' which, as the name suggests, focuses on his romantic relationships. Also, 'The Legend of Future Trunks' is a must - read as it expands on his character and his place in the Dragon Ball universe.
He becomes more resourceful. In his own time, he's used to a certain set of circumstances. But during time travel, he has to adapt quickly to new situations and find ways to use the resources available in the past. For example, he might have to figure out how to use different senzu beans or power - up techniques that are new to him.
One common theme is time-travel. Since Trunks is known for his time - traveling adventures, many fanfictions explore this aspect further, like dealing with the consequences of changing timelines.