I have the Focus Handwheel 2 and an Osmo Pro which works well but I have seen a pic on a dealers site with the the full size remote module, with handwheel, attached to an Osmo.  What does the remote module offer that the handwheel doesn't? (The pic is the middle one below the description of the cable)

Focus module and  Osmo

DJI Focus Handwheel 2 is the new-released product which is only available to Osmo Pro/RAW and Inspire 2, while the focus you mentioned is the previous product which is available to many DJI products like M600, Ronin, Inspire 1 and Osmo Pro/RAW and so on. For the previous version, the aperture, focus or zoom can be switched via buttons in the Focus, while the Handwheel can only be switched via APP.