For each object in Motion, whatever you would like to have to be editable in FCPX, find that parameter and right click on it. At the bottom of the popup menu will be the Option to Publish that parameter. You can check on it in Motion by clicking the Project layer at the top of the layers list and click on the Publishing tab. That is the list of editable parameters you will have in FCPX.
Warning: You cannot publish keyframed parameters. They simply will not work in FCPX. You have to do your keyframing in FCPX, or you have to find another way to have keyframed animations go on "behind the scenes" that will "blend" with the parameters you publish.
When you add a Drop Zone, the "source well" will automatically be published... but only the source well. If you plan to be able to have the Pan and Scale be available, you will need to publish those separately. The Pan and Scale of the Drop Zone affect the positioning of the media within the bounds of the Drop Zone (however you have it laid out). If you want to be able to publish the position and scale of the DZ, then you would publish the Properties > Transform parameters for that (DZ) object. These are two completely different aspects!
Once you get all your parameters published (or while you are publishing parameters) you can reorder them in the Project Publishing pane by clicking on the names and dragging them into the order you would like to have in FCPX. You can also rename all the published parameters by double clicking the name and typing in a new name. Be mindful that you don't really have a lot of space (FCPX will cut labels off if there's not enough room) — so keep them short. [You won't be able to rename the Drop Zone label however... go figure...]
