Quick question, I figured out my MC's but...

[Prince of Spires]

You simply make them different by writing them different. You didn't mention gender. Make one male and one female. Or make one impulsive and one calm and composed. Or alternatively make them the same person and just write 2 stories with the same MC. It doesn't matter. Just write.

 

[WonderingSword5]

You simply make them different by writing them different. You didn't mention gender. Make one male and one female. Or make one impulsive and one calm and composed. Or alternatively make them the same person and just write 2 stories with the same MC. It doesn't matter. Just write.

So if I write them as two different stories with the same MC, how could I explain the MC being both Japanese and white?

Also for another character in the story, this female fighter who's supposed to be the daughter of the Monkey King, would it be offensive to Chinese culture if she was born and raised in the US, and studied kickboxing and Brazilian jiu-jitsu, rather than being born in China and studying kung fu?

 

[CupofJoe]

I don't like writing this, but you seem to be finding lots of reasons not to do this.
The blank screen and empty page can be terrifying.
To wander around on what others have said...
Of all your ideas, pick one thing that interests you and write one version of one story and see where that gets you.
You may find new ideas and concepts appear to you, while other fade away.