No worries, and yeah they will all sound different. I have shorty headers, EFI. and the BJ's 3". I will say I do not like loud exhausts nor the 'muscle car' sound so I was a bit concerned but it sounds great without being obnoxious at any speed. I had a Borla muffler on earlier before I went to a stock style muffler because it sounded like hell and crazy loud.
I have done a bunch of custom exhausts myself, and while its a simple setup I think the price is very reasonable. Once you price out the mandrel bent SS piping and the magnaflow muffler it's not much of a markup so that's why I ended up pulling the trigger.
My only complaint was that the clamps were not great because the nuts pull into the lower clamp. Either address with some thick washers or just toss them for better clamps. From a stock replacement setup to this was an absolute necessity, especially after EFI you can tell this engine needs to breathe. I consider the 3" exhaust a must-have now on a JGW.