By default creates camera looks down in -Z, good when your world spans in XY plane. And TUniversalCamera.NavigationType is ntNone, which means that no automatic way to move camera in the world is possible, you want to program your own movement for 2D.
Sets 2D projection. By default (see CalculateProjection) our visible X range is [0..window width in pixels], visible Y is [0..window height in pixels].
Sets RenderStyle = rs2D by default, which makes it possible to place the scene manager rendering in the middle of other 2D controls (for example, over some 2D background and before some 2D buttons.)
Sets Transparent = True by default, which means that background underneath will be visible. Useful for 2D games where you usually have an image or another background underneath, like TCastleImage or TCastleSimpleBackground.
When True, the size of the world visible in our viewport will depend on scene manager size. ProjectionHeight is ignored then. When False, ProjectionHeight is used to determine the height of world visible in our viewport (width is automatically adjusted to follow aspect ratio of viewport size).