One possible plot could be that the Child Emperor, with his high intelligence and various inventions, is initially intrigued by Garou's self - proclaimed 'hero - hunting' ideology. They might have a series of battles where the Child Emperor uses his technological gadgets to counter Garou's martial arts skills. Eventually, they could find some common ground in their views on the nature of heroes and villains, leading to an unexpected alliance or at least a mutual understanding.
It's really hard to say. The Child Emperor has his amazing technology and intelligence on his side. He can create all sorts of gadgets to attack and defend. But Garou is a really tough fighter with great martial arts skills and the ability to quickly adapt in battle. If the fight is in an open area, Garou might be able to use his speed and agility to dodge the Child Emperor's attacks and get close enough to land a powerful blow. However, if the Child Emperor has time to set up his defenses and traps, he could potentially wear Garou down. So it could go either way depending on the circumstances of the fight.
One possible storyline could be that Goku is accidentally transported to Alucard's world. They start off as enemies but then gradually learn about each other's powers and come to respect one another. Another could be that a powerful villain manipulates them into fighting each other. In this case, they might realize they are being used and team up against the real enemy.
It's really hard to say. Goku is extremely powerful with his Super Saiyan forms and incredible combat skills. But Alucard has his vampiric powers like immortality and the ability to control shadows. In a fanfic, it could go either way depending on how the author wants to write it. Maybe if the author wants to emphasize speed, Goku might have an edge. But if it's about dark, mysterious powers, Alucard could come out on top.
There could be a storyline where Issei challenges Goku to a friendly sparring match to test his own limits. As they fight, they exchange techniques and learn from each other. This could lead to Issei unlocking new forms of his own power, inspired by Goku's Super Saiyan forms. And Goku could also gain new insights into combat from Issei's more unorthodox fighting style.
It depends on the rules set in the fan - fiction. If it's a battle based on strategy, Issei might have a chance. He has shown to be quite cunning in his battles. But if it's a pure power - based fight, Goku has the upper hand. His years of training under various masters and his Saiyan heritage give him an edge. Also, Goku has experience fighting opponents much stronger than himself and finding ways to overcome them.
One common theme is the clash of different power systems. Star has her magic from the 'Star vs the Forces of Evil' universe, and Goku Black has his Saiyan powers from Dragon Ball. Another theme could be the exploration of good and evil. Goku Black is a villain, so stories might focus on how Star and her friends deal with his malevolence. Also, the idea of interdimensional travel can be a theme, as Goku Black is from a different universe in Dragon Ball and would have to cross into Star's world.