If your looking at at the facelifted models. The range is much simpler to understand as the original shape has so many variations.
Facelifted models are far as I understand:
RS 265 Cup
RS 265 Cup Premium
RS 275 Cup Premium
RS 275 Trophy
RS 275 Trophy R
I am not sure about 100% specifics of each, very minor changes.
All face lifted cars have LSDs, the same infotainment system, brembo brakes etc.
Standard Cup comes with just the car (Recaros or big leather heated seats being optional). Premiums add recaro, leather and bigger wheels standard.
Trophy gives same as premium, but you get alcantara everywhere, titanium exhaust and a small power boost.
Its a buyers market at the moment. But it will still depreciate. However if you want to sell in the future, liquid yellow colour, with recaros in premium or trophy spec will be most desirable for reselling.