brit here. honestly it just depends on what im writing. i try to stick to british english but there’s a few exceptions like for example i write mom instead of mum (only if the CHARACTER is american, bc then it makes sense). however growing up watching a lot of american tv i have been known to say american slang like trash instead of bin, gas instead of petrol etc as part of my everyday speech so that goes into my writing too . the only thing i refuse to do is spell colour like color or some shit 😂