A Decat to Std Catback would sound great IMO
Should also provide the same performance as any aftermarket TBE on a K03 motor.
The gasses cool as they travel through the system and effectively shrink, not requiring such a large diameter to travel at the same speed. The Std cat back is 2.25" internal diameter on a GTI (prob same on VRS) and should not be restrictive.
It might be worth getting your MOT done just before you have the decat installed