See declaration of TStringGrid:
{ TStringGrid }
TStringGrid = class(TCustomStringGrid)
protected
class procedure WSRegisterClass; override;
public
property Modified;
published
property Align;
property AlternateColor;
property Anchors;
property AutoAdvance;
property AutoEdit;
property AutoFillColumns;
property BiDiMode;
property BorderSpacing;
............. etc.
As you can see, it is the same, only publishing public properties of ancestor. Published properties are visible in Object Inspector.
You can eventually use TCustomStringGrid if you will create it in code.