In PA, the legislature did change the laws to facilitate mail in voting. Problem is, it required a constitutional amendment, to be voted on by the people, not just a law enacted.
Yes, because states' election laws are tied to the US Constitution, they will vary. In PA, their election laws state that changes are presented to a public vote, which wasn't done. So the changes by the Executive and Judicial branches of government don't mean squat. Well, they do make the election UNLAWFUL from the get-go.