TestPointCloudStyle, which allows you to set a point cloud size in model units rather than pixels, works in Rhino 8. In Rhino 9 BETA, the command is available but appears to be broken. Nothing changes when it is set to enabled. This is not the first time it broke, it happened once during the Rhino 8 cycle too (see https://mcneel.myjetbrains.com/youtrack/issue/RH-78714).
I realise that it is a test command and should not be relied upon but it’s so useful that it should really be an official feature. For the type of point clouds that I work with (Aerial LIDAR, relatively sparse) it’s extremely important. Without it, you have to choose between points in the foreground being so small they are effectively invisible, or points in the background being massive and bloated.
I don’t know if it’s too late to properly integrate it into the display mode settings in Rhino 9, but if not it would at least be great if the test command kept working for those of us who use it.