I'll preface this by stating that I'm a complete beginner.
Re different sites listing different notes - this happens because sometimes it's peoples best guess and also because companies release varying degrees of information about the notes in their fragrances. To add to the confusion different notes can be released for the same fragrance due to different marketing approaches wanting to focus on different aspects of a fragrance. I can't comment on Mitsouko specifically.
Re relativity of notes - yes from the fragrances I've experienced so far relativity plays a part. Relativity both in terms of the other notes employed but also the volume of each that's used.
Re evaporation - I don't know to what extent the rate of evaporation can be manipulated but I suspect it varies greatly depending upon the chemicals/oils involved.
Anyway that's my 2 cents, I'm sure others will be able to chime in with much more specific and scientific information.
edited to remain on topic, I must have been on something earlier!