Q: How do you differentiate your characters while you’re in their views? Do you use different language? Sentence structures? Do your characters notice different details? What else?
A: In my WIP, I have two POV characters: a British girl and an Asian young man. I find myself, when writing from their respective POVs, using different word choices, sentence structures, rhythms, etc. But the differences do not end in the mechanics or descriptions alone -- it's also in thoughts, observations, philosophies, etc. I have to describe the world and what happens through these character's eyes and minds, and they are very different characters with very different backgrounds.
I think as long as you have different characters and you get to know them well, there should not be any problem distinguishing them. It comes naturally, simply because you're seeing the world through these different characters' eyes (and not as an omniscient narrator who has its own world view).