About the world. We know:
The red line isn't a continent but islands that are very close to each other
Oars epithet is weird unless there are actual continents in the other blues
The world is strange, but we have no evidence of it being any other way except our world perspective
The world is very dangerous for devil fruit users
We don't know enough about the war, other than the ancient weapons were used, and that it was the kingdom of D vs the world government. Or is it?
We don't know who owned the ancient weapons, only that after everything the kingdom of D managed to hide them.
The WG probably doesn't know what exactly poseidon did. Or else some word of the shirahoshi incident from 10 years ago would have raised an alarm.
Considering the power that maxim wields, as it was capable of obliterating an island, maybe it was partially built with ancient technology, but without it's regular power source or weapons, but with the thunder fruit providing those things.
The other thing that has been attributed the power to destroy the world is the quake fruit, and we have seen a few things able to raze an island, mainly the buster call, maxim, and the clash of the ice fruit with the magma fruit.
The secret of marijoa, something so horrible or precious capable of maintaining the celestial dragons at bay. And the op fruit being needed to access it.
We have an Adam tree. An eve tree. A tree of knowledge and fruits from the devil. Its too close to biblical to not be related.
Adam tree is very strong, and comes from a country ravaged by war
Eve tree is capable of very weird properties, like having shinning roots, and producing oxigen and the shabody resins.
The tree of knowledge didn't seem to have any of these properties. It could be an Adam tree that got bombarded beyond its resistence.
Fishman island weird… Everything came from the eve tree. As being the only place in the sea floor that gets sunlight thanks to it, it gets oxigen thanks to it, and it can be dry and have weather thanks to it. The island must have started as a little clump of earth that got into the bubble and started to grow when pieces ground and bubbles started to combine over the ages.
Fishmen from a story perspective seem to be the result of oda wanting to have sea zoans without breaking the devil fruit rules, as the most water related powers we have seen, ice, mud, snow, axotol and swimming, just skim the surface.
There might be a in story reason, if the creation of zoans is related to the creation of merpeople.
The great seastone mine has to be close to vegapunks lab.
The sky islands are weirder than fishman island, and yet, they probably predate the WG formation. They are related to how sea stone gets into the clouds, and gives them solid and liquid properties.
I feel like the Florian triangle mystery will stay that way, its just a mysterious sea monster
I'm just taking notes of stuff that I feel will have to be developed further in the future.