I think all policy will be divided into two classes. Those things Trump cares about, and those things he doesn’t.
The things he will be interested in are those things that either a) directly affect him and his businesses b) are splashy and exciting enough that they trend on social media, and so dealing with them can be used to feed his ego, immigration and building the Mexico wall fall into this category c) Involve negotiation or re-negotiation of agreements and treaties, because I suspect he actually believes his propaganda that he is a whiz at negotiations, and if we could just let him loose and give him a military to use as leverage, he will be put America on top and take the rest of the world to the cleaners. Everything else including the majority of the day to day stuff involved in being president and keeping the government running falling into the category of things he doesn’t care about.
For those things, he will let Congress, and his subordinates do what it wants without making use of the Bully Pulpit, and sign or veto the legislation based on whatever the majority of the Republicans want. for these things it isn’t worth the effort to come up with his own policy. If things go sour he will find someone to blame in his administration and fire that person. I expect at least 50% turnover in the cabinet and upper executive staff by the end of the term.
For the things he cares about he will attempt to rule through fiat, declaring what needs to be done and expecting everyone else to fall in line. If they don’t he will call them bad names, and do whatever he can to damage them, and in the meantime carry on ignoring congress and issuing executive orders to get what he wants done until the supreme court gets together and tells him to knock it off.