Exhaust headers, x pipe on the way

Want to run the exhaust out the back. What combo should I go for with this on the way.

I ordered the clifford performance headers with x pipe.

Single flowmaster muffler or go dual?
I know there is spacing issues and things to look for when running them through.

Will it be better with the single muffler with dual Inlet/outlet?

Also want to reduce the noise in the car. And get the throaty muscle car sound outside the car.