I’m answering these together because the root of both questions is basically the same.
And here’s the
hopefully not too harsh sounding answer: Write what you want to write. If you feel pressured to include a certain ‘type’ of character, or feel like the inclusion police are going to come to you if you don’t make sure to have diversity (of all types), you are not ever ever ever going to do your best writing.
Your writing is your writing and no one else’s. Any external influences you allow to dictate what you write will very likely have an adverse effect not just on writing, but how you treat the subject matter and/or characters you’re feeling pressure to write about.
This isn’t to say you shouldn’t keep an open mind to new ideas as they come, or to ignore that the majority of fiction (in English) isn’t necessarily the most diverse writing there is. The fact that you are asking these questions and are concerned shows you’re awareness of the issue and desire to possibly effect change — and that’s great.
However, no writer should insert a character who is of a race, gender, sexuality, weight, etc different from what they initially intended solely for the purpose of trying to create diversity.
What it really should come down to is this: Write people. Don’t write a trans character. Don’t write a black character. Don’t write a gay character. Don’t write a feminist character. Don’t write an overweight character. Don’t write someone who is all or none of these things. Write PEOPLE.
Once you’re written a fully developed, well-rounded person, you can go back — if you want — and see if changing their race, or gender, or sexuality might add some dimension or provide for a better storyline, or offer more possibilities for a dynamic plot, and adjust for those on rewrites.
tl;dr — Don’t write character types, no matter what pressure/guilt you feel. Write PEOPLE who are well-rounded and fully developed, and after a while they’ll come out as being diverse not because you feel pressure to make them as such, but because that’s how real people are.
Hope this helps.