Hi MT3, welcome!
I thought I'd add my view to your conundrum...
I had a GTI MK7.5 (non-performance) and I was looking for a bit more from the exhaust. I did quite a bit of research and ordered the Clubsport S backbox as it sounded great on videos (never had the chance to hear one in the flesh). Clearly I didn't do quite enough research as there were some very slight changes to the rear diffuser on the 7.5 facelift meaning that it wouldn't fit!
Not to be defeated, I then looked for alternatives and found the remus backbox delete. Again, I thought it sounded great on videos... Motech have quite a few on YouTube. This option had various clamps which could be adjusted to fit the mk7 or the 7.5 so I went ahead and ordered one at Awesome GTI near Manchester.
In the meantime, I saw a good deal on a Clubsport so I traded in my GTI MK7.5. I fitted the Remus backbox to my Clubsport about 6 months ago - see pic.
For me, it all depends on the type of driving you do. My commute is mostly country roads so I enjoy the burbles and pops from my exhaust. Particularly the fireworks in DSG Sport or manual. Driving with constant revs over 3,000 on the motorway though is quite tiring as there is noticeable drone. I did a long journey a few weekends ago and was tempted to go back to my original exhaust!
If I had a MK7, I think I would go for the Clubsport S backbox as it gives slightly larger tailpipes than the MK7 (same size as Clubsport and 7.5 and slightly smaller than the remus), with a better note and (I assume) limited drone given it is OEM. It was about £300 from a main dealer excluding fitting as far as I remember.
Whilst I don't have any experience of it, there are a few guys on here with the VagSport/ Progressive Parts res delete and are very happy. They have also commented that there is no drone so it might be an option if you do lots of motorway driving. It's also much cheaper I think (<£200).
Finally, if you do actually have a MK7.5, I saw this advertised today which seems like a good price (Awesome GTI ebay shop). Clearly I can't comment on how that might sound though - I'm guessing loud!
https://www.ebay.co.uk/itm/Milltek-Cat-Back-Non-Res-System-VW-Golf-Mk7-5-GTi-incl-GTi-Performance-Pack-/264043426589?fbclid=IwAR3LePn85zhjGsPrWzvauovnlrLJLPylhRSqWRod8N5jWkRcS2XBC36jfDA Have fun with the youtube searching and let us know which route you go down.
Andy