As an example, the UK is formally considered a unitary state but in reality its subregions enjoy a lot of autonomy and are able to pass laws of their own. On the other hand Russia is formally a federation but in practice all of its states are centrally controlled from Moscow and the legal system is more or less unitary across the entire country.
Does there exist a ranking of states based on how unitary/federalized they are in practice? I suspect Vatican would be the most unitary state while Switzerland the most federalized one, but it would be interesting to see how other countries are ranked.