Does Rajkumar Hirani choose actors according to the script?

Rajkumar Hirani has given final narration to Shah Rukh Khan for an upcoming project. The movie is said to be a social- comedy that would showcase journey of a man undergoing immigration from India to Canada. Now we all have seen his wonderful work with other projects like PK, 3 idiots and Sanju recently. But did you think why he has chosen SRK for this project? For a long time I thought he had a good work connection with Amir Khan as they have worked on some great message giving movies, which is Rajkumar's forte. Then we saw him pairing with Ranbir Kapoor for Sanju which was a perfect fit for both the actor and the director! So what made him choose SRK for this particular role? I believe he looks into the character deeply and then goes on to choose the right cast for it even for the side roles. He focuses on the details a lot! Everyone is super excited to know more regarding this project and SRK's role in it.