As an owner of a Sebo G1, I can confirm that the height of the cleaning head does not adjust until you put the machine in the operating position, but the cleaner does not need to be turned on. If I hadn't bought a G1, I would have been interested in the Evolution, but I don't see the need to get one as I am more than happy with the G1 which has all the benefits/disadvantages of the X series, but with the manual height adjustment which I pesonally prefer to the automatic system.
Most of the parts from the X series are compatible with the G1 apart from the exhaust filter which is a different design but more effective at stoping the carbon dust emissions than the sponge type filter fitted to the X models.
I have also owned a Sebo BS36 from new but never found it very effective even with the optional hard brush strip installed. The Evolution seems to have the same type of single brush strip that the BS36 has which doesn't seem as effective as the brush roll fitted to the G1, Felix and X series. Had the Evolution been fitted with the same brush roll as the X models, I may have been tempted, but my next Sebo purchase will probably be one of the new Airbelt E models.
Have you seen the video below? The bloke acts like a right knob, but he seems to know what he's talking about.