I dont think the plan is for both him and Thiago to play. It will be either of them but not both because they do similar things and Thiago is the best at what he does.
He seems to be more of the Gini mold where in he is press resistant, can turn with the ball and prefers to play short and safe passes all though he has the ability to pick a 40 yarder to switch the play. The most common complain from fans of his previous clubs is that he can be too safe. Its something that has been a common stick to beat Hendo/Gini with but I think that is exactly what we have missed in midfield, some semblance of control and protection and hopefully he provides that in the absence of Thiago.
I don't think there was is any plan, we were desperate to bring a midfielder in, and we found one. Think normally we would give him a game or two, see how he does, then design him a training plan to get up to speed. But with the amount of injuries we have, he'll likely play more sooner.
Not too fussed about him not making it at Barca and Juve, Salah was written off too, before he joined us. I actually think a tidy ball-hugging midfielder will do us good, we'll be more likely to play through the middle and cut out those useless crosses into the box we seem to be fond of. Biggest risk is that he's not actually over those injuries that kept him out at Juve.