In RVIZ, you can add Occupancy grid display and subscribe to /map topic in your case.
In rtabmapviz, you can do "Window->Show view-> Graph view" to show a 2d view with the grid. To show in 3D Map panel, you should enable "Preferences->3D Rendering->Grid Map Assembling->Show in 3D Map view"
You can add
<param name="Grid/FromDepth" value="true"/>
under rtabmap node to create the 2D map from the depth image projection instead of laser scan (until you find a solution of inf values in the scans)