The 'Search for the Vanished' is also a common trope. Characters in the fanfics try to find a way to reverse the Snap and bring back their vanished friends and loved ones. This often leads to epic adventures and new alliances. It gives the writers a chance to explore different magical or scientific solutions.
One of the key aspects of the 'World War Z' novel in terms of TV tropes is the use of the 'Zombie Apocalypse' trope. It presents a world overrun by zombies in a very detailed and global scale. The novel uses the 'Everyman Hero' trope as well, with ordinary people rising to the occasion to fight against the undead. For example, the various characters from different parts of the world all have their own stories of survival and resistance.
In this type of fanfic, the Infinity Stones could have a very different effect in the Harry Potter universe. For example, the Time Stone could be used to reverse dark spells or resurrect fallen wizards. However, the Stones' power might also be limited by the magic rules of the wizarding world. The fanfic could delve into how the characters from both universes adapt to the presence of the Stones and how they use or misuse their power.
Definitely. The Infinity Gauntlet comics came out earlier and laid the foundation for the concepts and characters seen in Infinity War. There are some differences, but the comics serve as a precursor.
Avengers Infinity War is largely based on the Infinity Gauntlet comic. Many key elements and plot points are drawn from it, but there are also some creative adaptations and additions to make it work for the cinematic universe.