World Building

[DeviousColony69]

It might sound flippant, but how about you do a roll? Make fate take its course? You can do it through dice or a random number generator. Just list out the 'whens' that you think are applicable to your story, do the roll, then you are done.

At some point, I am imagining the MC conquering both worlds. Instead of another world, how about parallel universes, or alternate reality?
Parallel Universe 1 has magic and science while Parallel Universe 2 has magic only.
Alternate Reality 1 has an Albert Einstein, while Alternate Reality 2 doesn't.

Mixing both parallel universe and alternate reality seems like a good stronghold for my writing XD

 

[WinterTimeCrime]

In one of my books, I focused a lot of world-building on lore and weapons (as it was a transmigration novel where the new surroundings needed explanation and had many intense fight scenes). In contrast, my other book focuses on organizations, individual status, and different cultures (as it's about space travel and multiple things are building upon one another and ever-expanding).

Read books in a similar genre or following an equivalent situation your character is facing and see how they keep the story moving. It's really on a case-by-case basis as some worlds need not follow all of the 'world-building' aspects to actually world-build.