Mac Performance Cat Backs

I’ve always loved mustangs and finally got one. Now I don’t know much about cars, just the basics. When it comes to performing mods were I am lost. I have installed CAI’s because it’s fairly easy. I wan’t to continue doing my own mods and saving the money. But I am lost with exhaust systems. I’ve been looking at the Mack Performance Cat Backs and there at a good price, and they look like they go connected to the cats with nothing else needed. Where I am lost is with all this Y’s and H’s. The Mac Performance Cat Backs I have seen don’t come with neither. I have a 2002 Mustang V6, the exhaust from the manifolds back I notice that the exhaust comes out from both sides down with separate pipes to the cats down to the 2 mufflers then after the mufflers they go to a y pipe to one pipe and out to the rear.

Now my question is, when installing the Mac Performance Cat Backs is necessary to have the Y or the H pipe or can I just install it to the cats down to the rear with installing the Y pipe and H pipes?

Thanks