For my 2 cents, as a zfs shared volume admin, think carefully about why you want zfs. And this is not a knock on ZFS--I love it and use it myself for both workstation, laptop, and file server.
The default zfs installer setup is challenging to administer manually. Yet a manual install does require a good deal of zfs and command line experience.
Doing your option A will require manual zfs. I think that B will also. It is my understanding (though I've never used it) that the automatic installer has a preset list of datasets that it uses, with not many choices to deviate from that setup. It has been discussed many times on the ZFS mailing lists.
The definitive guide to Ubuntu root zfs manually installed is by Richard Laager, available on the OpenZFS website. However, even with this guide, you will need to learn a substantial amount about ZFS. Remember, it is a top end enterprise file system, with sysadmins as its target audience. Its entire structure is different from traditional file systems.