When it comes to what races you’re going to have in your story it kind of depends on where it’s set I guess.
Like, if your story is set in London it’s freakin weird not to have any Indian/Pakistani or black people in it. Less than 60% of Londoners are white, so a London-based tale featuring only white people is just dumb. But you go out to the East Midlands and it’s something like 90% white, so in a story of 12 people it’s entirely possible they’re all white folks.
Where is your story set? If it’s North Dakota, your characters should probably be pretty white. But if it’s in Dallas, the population of which is 25% black and also something like 42% Latino, you’re going to want to reflect that if you want any sense of verisimilitude. It’s not about it “feeling like a checklist”, it’s about it feeling like the world we live in.
As for the question of sexuality, why wouldn’t you have at least 3 lesbians in any story you write?
- Women sense my power and they seek the life essence.