In the latest version (build 2016.10260), bars overlap each other a lot when the style is side and BarWidthPercernt is 100%. Instead in old version (build 4.1.2015.05144) all bars are more or less adjacent to each other as do in TeeChart VCL. 
I have attached a simple code to reproduce the problem:
private void InitializeChart()
        {
            Steema.TeeChart.Styles.Bar bar = new Steema.TeeChart.Styles.Bar(tChart1.Chart);

            bar.Add(0, 10, "Cat1");
            bar.Add(1, 20, "Cat2");
            bar.Add(2, 30, "Cat3");
            bar.BarWidthPercent = 100;

            Steema.TeeChart.Styles.Bar bar2 = new Steema.TeeChart.Styles.Bar(tChart1.Chart);

            bar2.Add(0, 30, "Cat1");
            bar2.Add(1, 10, "Cat2");
            bar2.Add(2, 20, "Cat3");
            bar2.BarWidthPercent = 100;
            tChart1.DoubleClick += TChart1_DoubleClick;
        }
Also,  I have added the same code in Teechart VCL:
uses Series;
var series1,series2 : TBarSeries;
procedure TForm1.FormCreate(Sender: TObject);
begin
series1 := TBarSeries.Create(self);
Chart1.AddSeries(series1);
Chart1.View3D := false;
series2 :=TBarSeries.Create(self);
Chart1.AddSeries(series2);
series1.AddXY(0,10,'cat1');
series1.AddXY(1,20,'cat2');
series1.AddXY(2,30,'cat3');
series1.BarWidthPercent := 100;

series2.AddXY(0,30,'cat1');
series2.AddXY(1,10,'cat2');
series2.AddXY(2,20,'cat3');
series2.BarWidthPercent := 100;
end;