As far as limits to voting, I would argue (and this would count me out

) that only land-owners get to vote. By owning land, you’re making an investment in the country, and have a stake in it’s success, because failure and the eventual collapse of your government may indeed mean the loss of your land, among other things.
As far as the scope goes, referring specifically to the United States, I would agree. The Federal government isn’t meant to be a government over millions, but simply a government over 50, by the current count - a government of governments, but not necessarily a government governing governments.
Any real political decisions ought to be made at the lowest denominator. The decisions that affect the residents the most ought to be made the lowest level. As far as a possible example goes, I would love for the Feds to tax the various states x amount of money based on population, while the various states can decide how to raise that money…aka, remove all other taxes, except tariffs)