I've been using an Apexi exhaust control valve for nearly a decade. It looks naff using a bung, and also doesn't allow you flexibility to open it up without pulling over. Which is a bit shit, like E85. Pulling over to top up race fuel while you remove the exhaust bung
At 60mph I can barely hear the exhaust when its closed. It's still loud as hell when open.
I understand everyone likes to promote their own choices on their cars, but I've seen some people argue a bung is better than a valve. So many advanced cars use these, electric versions, you don't see top end manufactures handing you a bung with your exhaust.
I have a straight through 4.5 inch exhaust single box, its loud. Such an improvement. Located in my midpipe. I would only recommend buying an Apexi version, and call me old fashioned but I prefer the mechanical latch rather than a switch and motor sat on the exhaust pipe.
https://www.apexi-usa.com/products/apexi-ecv-exhaust-control-valve-flange-type-80mm