I have a 2016
Cupra and the acc system on all mk3's are the same.
You can choose any speed between 1 and 100 m/h and it will bring you to a complete stop - the only difference between the different models is that for 2017 going forward it will hold the brake for you once stopped. On pre facelift models it stops the car and then you have to hold the brake until the car in front starts moving again. You can then just release the brake and re activate the system without touching the throttle.
The sensor used for the acc system can "see" 300 meters forward hence the speed limit of 100 m/h. The limit is the same on most VAG cars with the exception being the all new vw coupe that uses another sensor and in connection with cameras will allow acc up to 210 km/h.
It is similar for other brands i.e. both Mercedes and BMW have limits at 200 km/h for the acc.
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