One common theme is the rivalry between Dib and Zim. It's always a central part of these fanfics as their battle of wits and attempts to outdo each other.
In this fanfiction, Dib could find himself in a situation where he has to rely on his wits more than ever. When meeting the Tallest, he may discover some secrets about the Irken race that could change the whole dynamic of his fight against Zim. The Tallest might underestimate Dib at first, seeing him as just a human child. But Dib, being Dib, would use this to his advantage. Zim would be his usual self, trying to prove his worth to the Tallest while also trying to stop Dib from ruining his plans. It could be a really interesting exploration of the characters' relationships and the power dynamics in the Invader Zim universe.
One popular 'curious dib invader zim fanfic' is 'The Dib and Zim Adventures'. It often features unique takes on their relationship and new adventures in the Irken universe.
Dib in this fanfiction is the curious and determined character. He is the one who will dig deep into the secrets of the Tallest. His role is crucial as he might be the only one who can see the real danger they pose. Zim, well, he's the chaotic element. He's not really on Dib's side but also not fully on the Tallest's side. He's just out for himself. The Tallest are the overarching antagonists. They hold the power in the Irken world and their actions drive the plot, whether it's through their plans for Earth or their relationship with Zim.
It depends on how you look at it. Some fans consider the comics canon because they continue and enrich the storylines from the show. However, others might have reservations based on personal interpretations.
You can start by finding a collection or anthology of Invader Zim comics. Many bookstores or online platforms sell them. Then, just open the book and start from the first page.