

what they basically say is that (and this is only valid for people using tor or mullvad browser with stock settings) if everyone has the same fingerprint, and if you dont sign in to anything else, they basically look same to the websites, so you dont have to use some privacy frontend, it is ot adding in any benefit. However, these conditions deffenitely are not that easy to meet for day to day use.
many have answered that as a concept, it is made up. But it is arguably the most real (and important) thing in all of physics (or maybe action, which is also some function dependent on energy). the money comparison is fine, if we have different forms of denominations of money (currency notes (different amounts), gold coins, etc) we have different forms of energy quantas.
Here is a viewpoint to understand - almost everything acts in a way to minimise total system energy. this can be (almost) made valid all the time if you include some probablistic factors. (If we take thermodynamics (which is by definition study of dynamics of energy(and heat, which can be considered as some kind of raw energy), then we include entropy, which is basically finding how many ways can a particular energy can achieved.). This is not a very rigorous way to put it all, but basically all of physics basically works on energy. Forces are basically caused by some kind of gradient in energy.