The flocked ones are the ones that are velvety instead of the plastic which gives a bit more realism. I have the shell ones and they work fine, the only reason I went for shell decoys is the take up less space for carrying as they can just stack on top of each other. You don't need many to start go for say 10 and then you replace them with real ones as you kills progress.
In terms of patterns the most important thing to remember is they land coming into the wind so the front of the horsehoe points into the wind and ideally you position your hide along a hedgeline that gives you straight i