Well, it could vary a lot. In some fanfics, Bardock might be reborn with new powers or a different destiny. Maybe he gets to change the future of the Saiyan race. But it really depends on the author's creativity.
Obviously, Bardock is one of the main characters since it's about his rebirth. Goku might also be involved as Bardock is his father. Vegeta could potentially show up too, as he is an important Saiyan in the Dragon Ball Z universe.
Dragon Ball Z is both anime and manga. The anime was adapted from the manga and they share the same story and characters, but presented in different mediums.
In general, it depends on your perspective. Some might find it inappropriate as it can be a rather odd and perhaps not in - keeping with the traditional values of the Dragon Ball Z series. However, in the world of fanfiction, there is a wide range of tastes, and as long as it doesn't cross into truly offensive or unethical territory, some may consider it a creative, if strange, exploration of the characters.
Towa can play a significant role in fanfiction. She might be a central villain, driving the plot forward with her evil schemes. For instance, she could be planning to disrupt the time - space continuum in a fan - created story.
In fanfiction, Towa in Dragon Ball Z often has various interpretations. She is a complex character. Some fanfictions might explore her backstory more deeply, like her relationship with other villains in the Dragon Ball Z universe. Her powers and motives can be further elaborated in these stories.
Sorry to disappoint you. The Dragon Ball Z manga is not ongoing. It had its own definitive ending, but its popularity continues through various forms of media and merchandise.