The main differences are in their expressions and some minor details of personality. In the manga, Deku might seem a bit more intense, while in the anime, he's sometimes presented a bit softer.
Perhaps Vegeta Jr could challenge Vegeta to a sparring match. Vegeta, being the proud warrior he is, would accept. During the fight, Vegeta Jr might display some new techniques he's developed, which could both surprise and intrigue Vegeta. And in the end, they could form a stronger bond as they realize they share the same values and goals as Saiyans.
Since we should avoid the 'lemon' aspect which is often not appropriate, in general Vegeta is usually depicted as a strong and proud character. He might be shown as a mentor - like figure to Pan in fanfiction. Pan, on the other hand, is often a curious and energetic character. In non - inappropriate fanfictions, their relationship could be one of mutual respect and growth, with Pan looking up to Vegeta for his power and experience.
Deku might be completely shocked at first. Since Bakugou has always been so aggressive towards him, he would never expect such a confession. He might just stand there, mouth agape, not knowing what to say.
His friends could come to the rescue. Bakugo, for instance, might use his explosive power to break into Toga's hideout. He's always been competitive with Deku, but he also cares about him deeply.
In 'deku meets future deku fanfiction', perhaps the future Deku warns the present one about upcoming threats. He could tell him about villains he'll face in the future and how to defeat them. This would give the present Deku an edge in his battles and also in his growth as a hero.
Well, obviously Deku in two forms - the younger and the older version are the main characters. The younger Deku is the one who is still growing and learning, while the older Deku has more experience.
As of now, Deku is very much alive in the manga. The plot hasn't reached a point where he meets such a fate. Usually, main characters like Deku have significant story arcs and aren't easily killed off.
A possible plot twist could be that Vegeta Jr is actually an imposter sent to deceive Vegeta. He could initially seem like a legitimate Saiyan but gradually reveal his true motives, which might be related to an enemy's plan to take down Vegeta.