Both are targets.
Both are doable targets.
And probably we will land both, if we manage to get rid of Joao Mario and possibly sell Vecino somewhere. With that being said, Barella is implied as a 'done deal' and SMS will depend on several factors.
We also want Kovacic, possibly if we manage to get rid of all the deadweight. The Rafinha 2018-2019 recipe. The one that failed, yes.
It might not be easy but it would be great to sign both Barella & SMS. I would not be content with only Brozovic, Nainggolan & Barella/SMS. I think that we need 4 quality midfielders, with few more quality squad players. SMS is an all-round quality midfielder and he would be good for us with aerial duels as well.
Brozovic, Barella, SMS, Nainggolan, Gagliardini, ?? should be great.