Alternative realities may have alternative people living in them - will they observe different laws of physics since their reality is not a sum of all realities

Alternative realities may have alternative people living in them - will they observe different laws of physics since their reality is not a sum of all realities, as opposed to ours? Or would they have the same conclusion about sum of realities? A) these realities can't have people - they're not real enough to be called that B) physics will be different - that would be a great scientific revelation C) physics will be the same - making the premise meaningless