Blackbeard's crew is also a diverse bunch. His more aggressive members like Burgess might be eager to start a fight with Luffy's crew. However, some of the more cunning members could be thinking of ways to use the situation to their advantage. They might try to manipulate Luffy or his crew into making mistakes. And if Blackbeard decides on a certain course of action, his crew would generally follow, but there could be some internal dissent depending on the situation.
It could also be that instead of fighting right away, there's a tense stand - off. Luffy, remembering Ace's past encounters with Blackbeard, would be full of anger and distrust. Blackbeard, on the other hand, might try to taunt Luffy, trying to get him to make a rash move. The situation could escalate slowly as they exchange words, with their crews on edge, waiting for the first sign of action.
Well, in such a fanfiction, Ace might be worried about Luffy. Since Blackbeard is a dangerous character. He could decide to go and find Luffy to protect him. Maybe he'd start looking for Blackbeard too, to make sure he doesn't harm his little brother.
Blackbeard would probably be very interested in the magic in the Fairy Tail world. He might try to steal some of the powerful magic items or learn magic for himself. He could see the mages as a threat to his plans if they oppose him, but also as potential allies if he can manipulate them. He would likely use his cunning and power - hungry nature to his advantage in this new world.
A cool plot would be when the Whitebeard Pirates meet Luffy while he's on a quest to find a rare Devil Fruit. They too are interested in that Devil Fruit for some reason. Instead of fighting over it, they decide to team up. Luffy's unique perspective and the Whitebeard Pirates' experience combine to create an epic journey filled with challenges and new discoveries.
In fanfiction, when the Whitebeard Pirates meet Luffy, they might initially be cautious. Luffy's reputation as a rising star in the pirate world could make them curious. Maybe they would test his strength. For example, some might engage in a friendly sparring match with him to see what he's made of.
They might have an epic battle to test Luffy's growth. Shanks could see how much stronger Luffy has become and be proud. Maybe Luffy will show off his new Haki abilities.