As for the quietness of the monitors. I am also very fussy when it comes to hiss and noise.
These DO have a tiny amount of hiss when no music is playing; most of this is pre-amp noise from having my interface cranked up. If I turn my interface to zero output, there is still a very small amount of hiss. If I put my head within 15cm of the speaker, I can hear it. If I don't do this I cannot So in my listening position (I'm close, around 80cm away from both cones) they are silent according to my ears. But someone OCD who puts there head right next to a monitor would comment on the hiss and they would be right. It's just that, real world, it's not loud enough to be heard from your listening position when there is no music on. You 100% cannot hear it if anything (even at low volumes) is actually playing.
As for their performance in this regard vs the other monitors.... I've seen on-line comments praising the quietness of the Neumanns but again I haven't a/b tested against the others on your list so I cannot say for sure if they are better or worse in that regard.
As to his moving around the room..... If he's moving around the room when he's playing then no near-field monitors are going to make him happy They will (by design) have a fairly narrow sweet spot and that is not very far away! In my (treated) room, they sound amazing 'where I sit'. If I move back 30cm they start to go off in terms of the stereo image.
But frankly if he's used to listening to music whilst moving around then stereo image might be forgiven in that case? If not, he really needs to just look at stereo speakers and an amp for a hifi which will be a bit more forgiving of his movement habits but of course won't be so good for mixing.