Welcome back Tony and a good choice
What was not to your taste with the S3?
Anyway, this isn’t an exhaustive list and I can’t help with part numbers or specifics but Clubsport differences:
Front bumper (fog light deletion too owing to additional cooling rad)
Rear spoiler
Rear valence
Side stripes
Different engine, same code as 8R but some ancillaries in a different position same as S3 and Cupra 300. The Golf R must have extra cooling hardware necessitating the changes. Regular GTI has smaller turbo and different internals, similar hierarchy to mk7 equivalents.
Different exhaust with oval tips.
Similar front suspension to 8R with negative camber.
357mm two piece drilled front discs and (I think) twin pot calipers
Slightly different rear suspension settings
Slightly shorter gearing IIRC
Nice fluffy alcantara seat trim which means no need for heated seats, they literally never feel cold.