In Mixed Reality (MR), users can collaborate efficiently by creating personalized layouts that incorporate both personal and shared virtual objects. Unlike in the real world, personal objects in MR are only visible to their owner. This makes them susceptible to occlusions from shared objects of other users, who remain unaware of their existence. Thus, achieving unobstructed layouts in collaborative MR settings requires knowledge of where others have placed their personal objects. In this paper, we assessed the effects of three visualizations, and a baseline without any visualization, on occlusions and user perceptions. Our study involved 16 dyads (N=32) who engaged in a series of collaborative sorting tasks. Results indicate that the choice of visualization significantly impacts both occlusion and perception, emphasizing the need for effective visualizations to enhance collaborative MR experiences. We conclude with design recommendations for multi-user MR systems to better accommodate both personal and shared interfaces simultaneously.