Based on Yoast SEO, it determine whether the title is too long based on its width instead of number of characters.

So, how to know the font, font size, and font style used in Google search results?

Also how to know the visible width for Google search results, from moz, it is said to be 600 pixels

procedure TMainForm.Button2Click(Sender: TObject);
var
  Bitmap: TBitmap;
  Width: Integer;
begin
  Bitmap := TBitmap.Create;
  try
    //  What is the font, font size, and font style used in Google search results?
    Bitmap.Canvas.Font.Assign(Self.Font);
    Width := Bitmap.Canvas.TextWidth('This is to test the title and to make sure it is not too long to be invisi');
    //  What is the max width of Google search results, based on https://moz.com/learn/seo/title-tag, it is 600pixels
    Application.MessageBox(PChar(Format('Title width is %d', [Width])), 'Information', MB_OK);
  finally
    Bitmap.Free;
  end;
end;