I've installed probably a half dozen or more of the Pypes Transverse system on F-bodies. I've always used the SGF70 on the F-bodies and X-bodies simply for the ground clearance. Once installed properly you can't even see the system on the car unless you crawl down on the ground to look for it.
The transverse from Pypes will be their race pro design. Depending on the engine itself and a few other things will really dictate how the system will sound for you. Especially how you configure the tail pipes.
Personally I haven't had one yet I didn't like the sound of and I've had them on everything from 350hp 400 Pontiacs, 400+hp SBC's to 500hp 455 Pontiacs.
Here are sound clips of my cars with the Transverse Pypes setup.
This is my 406 SBC, this one has headers
https://youtu.be/47HgejCVbFs
This is my firebird with a stock 400 with RA manifolds
https://youtu.be/uIFkggwDY-8
Here it is at the track.......driveby
https://youtu.be/er1z7PpqsnY
Here is my Z/28, with headers and the 2 1/2" tailpipes supplied by Pypes
https://youtu.be/5dTNw93VPEQ
I wanted the stock appearance so I installed the factory 2" tail pipes. Tamed it down quiet a bit
https://youtu.be/IZ0HlEY7b74
And just for giggles if you want to compare to a real factory exhaust, not reproduction. This is the born with original exhaust system still intact on the Z and still using the stock exhaust manifolds. Production date on the car is 12D of 68 so Chamber exhaust ceased regular production and it got what GM called a "deep tone" muffler without resonators. Later around March of 69 they incorporated some resonator mufflers to quiet the cars down even more.
As you'll see the "deep tone" muffler system without resonators, and all factory 2 1/4" crush bent piping with 2" tailpipes, it was rather "raspy" and in all honesty the Pypes system really isn't any louder outside or inside the car.
https://youtu.be/SDMeBoQpf58
And here is another SGF70 I installed on a customers car I was restoring. This 455 made 507hp/571tq through the stock RA exhaust manifolds.
https://youtu.be/AOqwz3QlO5k
To answer your other question, I would for sure go with a mandrel bent exhaust kit as suggested. Hardly any shops around that bend a system with a mandrel anymore so the kits have really been the way to go for many years. As far as Pypes goes, you probably won't find a better priced kit that is stainless steel with an X-pipe, and mandrel bent. There are plenty to choose from but most of them are well beyond the price point that Pypes has. And FYI if you don't want the X pipe they do make the transverse system with the H-pipe SGF40
If you want to go really cheap, Walker/Dynomax makes a very economical transverse system I've used in the past.
https://www.summitracing.com/parts/wlk-89021
What I like about this system is it uses the OEM style in and out muffler design meaning the over axle pipes are bent as OEM (unlike Pypes) so it opens up your transverse muffler choices. You can substitute the stock Walker fiberglass packed muffler this system comes with and install a Dynomax ultraflow transverse muffler if you desire and really hone in on the sound you're looking for. Since the system is so cheap you can afford to upgrade the muffler. I like this system with the Dynomax ultraflow welded X transverse muffler here....
https://www.dynomax.com/mufflers/ult...ded-x-mufflers