I can't speak to the first one, but AIUI the ZFS way of thinking about the second one is to create a new filesystem and just mount it where you want it, versus

I can't speak to the first one, but AIUI the ZFS way of thinking about the second one is to create a new filesystem and just mount it where you want it, versus "portions of the filesystem" which I doubt very seriously that ZFS allows. Bonus points that in that scenario, I would suspect the dedupe and compression would work even better since any such setup is likely to contain more homogeneous content (music, photos, etc)