Well, in the 'big mom is luffy's mom fanfic', they might have crafted a story where Big Mom is Luffy's mom. But it goes against what we know from the official 'One Piece' story. Fanfictions like this can be really interesting as they can rewrite the story in unexpected ways. They might have some interesting plot twists and explanations within the fanfic to justify this relationship, but it's not part of the main 'One Piece' universe.
One possible plot implication could be a change in Luffy's power source. Since Big Mom has such unique and powerful abilities, Luffy might inherit or be related to some of those powers in the fanfic. Maybe his Devil Fruit ability could be related to Big Mom's in some way.
As of now, in the manga, the identity of Luffy's mom remains unknown. There have been many theories and speculations among fans, but no official confirmation.
One common theme is family. Given Big Mom's large family in the original story, fanfics often explore family dynamics further. Another theme is power. Writers like to play with how Big Mom's power can be used or enhanced.
Often, these fanfics emphasize their power. Since both Kaido and Big Mom are extremely powerful in the original story, the fanfics tend to showcase their combined might or their power struggles. For example, they might be in a battle against a common enemy that only their combined strength can defeat.
I'm not sure about a specific 'Baron Tamago Big Mom Fanfic' that stands out above all others. However, you can try looking on fanfic websites. Search for tags like 'Baron Tamago' and 'Big Mom'. You might find some hidden gems there. Maybe start with the ones that have the most reviews or highest ratings.
It's difficult to say. Fanfic writers are known for their creativity and ability to come up with unique scenarios. But 'Kaido x Big Mom grandson' is a rather strange combination. If such a fanfic exists, it may be buried among thousands of other fanfics on different websites. You could try looking on popular fanfic sites like Archive of Our Own or FanFiction.net, but don't be too disappointed if you can't find it right away.
Big Mom herself is often a central and popular character. Her immense power and unpredictable nature make for interesting storylines. Writers can explore her relationships with her children and how she rules the crew.
One interesting story could be about a new crew member joining the Big Mom Pirates. They might face challenges in adapting to the strict hierarchy and unique rules of the crew. For example, they have to deal with Big Mom's mood swings and the various powerful members already in the crew.