(Chinese Grammar) Can 是(shi) be used to emphasize the following verb like 他是帅?

Nope, We have several ways of using 'is'.
But specifically talking about 是(shi) here, It's more used as 'Yes' to a answer.
I assume you were trying to ask (Is he hot / handsome ?) when you trype 他是帅? with a question mark at the end.
you could ask 他帅吗？ This is how you ask when your friend trying to introduce him