I've used ACF Pro to enable selection of one post type from another, along with some other custom fields. The main selection uses a Relationship field type, but there seems to be no control over how this appears and it's pretty clunky.
Is there a way of implementing a more traditional WordPress check box as seen in the meta boxes, rather than the ACF style selection box?
The ACF one also allows multiple selections in each row, I need it to be single selection per row.
If you are trying to get a dropdown list of a specific custom post types set your field type to Post Object and then set your Filter by Post Type to the custom post type you want displayed in that list.