Lo de tener varios TForm dentro de un TPageControl u otro Form es sencillo.
El wndForm principal tendrá un TPageControl
Código Delphi
[-]
Procedure TwndForm.CreateForm(FormClass:TFormClass; AParent:TWinControl; AColor:TColor; AFont:TFont);
Begin
With FormClass.Create(Application) Do
Begin
Color := AColor;
Font := AFont;
BorderIcons:= [];
BorderStyle:= bsNone;
Align := alClient;
Parent := AParent;
End;
End;
procedure TwndForm.PageControlOnChange(Sender:TObject)
begin
if (PageControl.ActivePage.ControlCount<>0) then
Exit;
case PageControl.TabIndex of
0:Begin
CreateForm( TForm1, PageControl.ActivePage, Self.Color, Self.Font);
TForm1(PageControl.ActivePage.Controls[0]).Show;
End;
1:Begin
CreateForm( TForm2, PageControl.ActivePage, Self.Color, Self.Font);
TForm2(PageControl.ActivePage.Controls[0]).Show;
End;
end;
end;
Espero te oriente en lo que deseas realizar.
Saludos cordiales