Up to you but I certainly wouldn’t risk leaving the connectors exposed. Two things electronics hate are dust and moisture. There’s a lot of scope for airborne contaminants under an engine bay, and moist air (of which there’s plenty overnight in winter) gets everywhere, even places you might think are safely tucked away. As for what to use, insulation tape would seem the obvious low tech solution if blanking plugs aren’t available.
I wonder, though, do you need to disconnect it at all? As I understand it, the objective is to run the car in
Cupra mode but without the
Cupra noise? Would it work if you set up individual profile with everything set to
Cupra except for sound, and set that to comfort?