It would be foolish to write Trump off as merely a figurehead
Based on the lack of both understanding of policy and an exhibited lack of desire to understand policy, I've seen a few people indicate Trump will be nothing but a figurehead president. The thought is that Trump will be trotted out for ceremonial purposes while Mike Pence and the cabinet make all the decisions.
While I understand the view behind this thinking, ultimately I don't think it is quite accurate. Trump's ego will never allow others to have the final decision and he'll lash out at anyone who attempts to usurp him. That's just who he is.
But that's not to say he'll be intricately involved in policy. He most certainly won't.
Trump will see himself as the Chairman of the Board. He'll see Mike Pence and the Cabinet heads as underlings charged with coming up with ideas, who then have to present them to him as the ultimate authority. And he gets to say yes or no and that's the final word. Problem is, his decision making is so clouded by his ego and his mood that his final say isn't necessarily rational at all. And whether or not a policy is adopted by Trump could hinge on how well the person flatters him.
Ultimately it's the worst of both worlds. A leader who demands ultimate authority and respect but has a contempt for the nitty gritty of the policy making process.