ready made cauliflower couscous or rice can be used - you can find it now ready made in almost all supermarkets here in the UK
I have used Jumbo/King or tiger prawns as they are called with shell and I have cleaned them all and left three with shell for decoration. I think you can buy the ready clean ones from the supermarket as long as they are big and juicy it’s perfect.
If you don’t have roast peppers which are normally found in a jar use fresh ones which you could roast if you want to for different flavour or simply cook the fresh ones with the Chorizo.
Chorizo goes very well with prawn but you can replace this with pancetta or any cooking meaty sausage.