I would pick everyone on defensive ability first. For me its the most important asset a player should have. Hull KR have , I think, the best squad of players for any side that has been promoted. They have good players with SL experience, Not seen the odds yet but I think with home advantage etc if I was setting the handicap I would say this match was will be off scratch.
For me Carney is a massive threat, if he gets a one on one close to the line there are not many who can stop him, they do not have to create an overlap, so hence my opinion that you mark him with Toupou. Bill scored a hat rick against Wigan last season when on the wing plus played his GF in Aus on the wing so not a position he is unaccustomed to.